Quinoxaline derivative, and light-emitting element, light-emitting device, electronic device using the quinoxaline derivative

ABSTRACT

It is an object to provide a novel bipolar organic compound. In particular, it is an object to provide a bipolar organic compound excellent in thermal stability. Further, it is another object to provide a bipolar organic compound which is electrochemically stable. A quinoxaline derivative represented by a general formula (1) is provided. Further, since the quinoxaline derivative represented by the general formula (1) is bipolar, the use of the quinoxaline derivative of the present invention allows fabrication of a light-emitting element and a light-emitting device with a low driving voltage and low power consumption. Furthermore, a light-emitting element with high luminous efficiency can be obtained.

TECHNICAL FIELD

The present invention relates to a quinoxaline derivative, and alight-emitting element, a light-emitting device, an electronic deviceeach of which uses the quinoxaline derivative.

BACKGROUND ART

Organic compounds can take various structures compared with inorganiccompounds, and have possibility to provide materials having variousfunctions by appropriate molecular design. Owing to these advantages,photo electronics and electronics which utilize functional organicmaterials have been attracting attention in recent years.

For example, a solar cell, a light-emitting element, an organictransistor, and the like are exemplified as an electronic deviceutilizing an organic compound as a functional material. These aredevices taking advantage of electric properties and optical propertiesof the organic compound. Among them, in particular, a light-emittingelement has been making remarkable development.

It is considered that light emission mechanism of a light-emittingelement is as follows: when a voltage is applied between a pair ofelectrodes which interpose a light emitting layer, electrons injectedfrom a cathode and holes injected from an anode are recombined in thelight emission center of the light emitting layer to form a molecularexciton, and energy is released to emit light when the molecular excitonrelaxes to a ground state. As excited states, a singlet excited stateand a triplet excited state are known, and light emission is consideredto be possible from any of these excited states.

Such a light-emitting element has a lot of problems which depend on theorganic materials. In order to solve these problems, improvement of anelement structure, development of a material, and the like have beencarried out.

As the most basic structure of a light-emitting element, the followingstructure is known: a hole transporting layer, formed by an organiccompound having a hole transporting property, and an electrontransporting light emitting layer, formed by an organic compound havingan electron transporting property, are stacked to form a thin film ofapproximately 100 nm thickness in total, and this thin film isinterposed between electrodes (see Non-Patent Document 1, for example).

When a voltage is applied to the light-emitting element described inNon-Patent Document 1, light emission can be obtained from organiccompounds having a light-emitting property and an electron transportingproperty.

Further, in the light-emitting element described in Non-Patent Document1, functions are appropriately separated. That is, a hole transportinglayer transports holes, and an electron transporting layer transportselectrons and emits light. However, various interactions (for example,formation of exciplex, and the like) frequently occur at an interface ofstacked layers. As a result, change of emission spectrum and/or decreasein luminous efficiency may take place.

In order to suppress change of emission spectrum and decrease inluminous efficiency which are caused by the interaction at an interface,a light-emitting element was developed in which functions are furtherseparated. For example, a light-emitting element has been proposed, inwhich a light emitting layer is interposed between a hole transportinglayer and an electron transporting layer (see Non-Patent Document 2, forexample).

In such a light-emitting element described in Non-Patent Document 2, itis preferred that, in order to more effectively suppress the interactionoccurring at an interface, a light emitting layer is fabricated by usinga bipolar organic compound which has both an electron transportingproperty and a hole transporting property.

However, most organic compounds are monopolar materials having either ahole transporting property or an electron transporting property.

Therefore, a bipolar organic compound having both an electrontransporting property and a hole transporting property has been requiredto be developed.

In Patent Document 1, a bipolar quinoxaline derivative is described.However, since their performances such as thermal stability are notsatisfactory, bipolar organic compounds having high thermal stabilityhave been required to be developed.

[Non-Patent Document 1]

-   C. W. Tang et al., Applied Physics Letters, vol. 51, No. 12, 913-915    (1987)    [Non-Patent Document 2]-   Chihaya Adachi et al., Japanese Journal of Applied Physics, vol. 27,    No. 2, L269-L271 (1988)    [Patent Document 1]-   PCT International Publication No. 2004/094389

DISCLOSURE OF INVENTION

In view of the aforementioned problems, it is an object of the presentinvention to provide a new bipolar organic compound, in particular, abipolar organic compound having excellent thermal stability. Further, itis another object to provide a bipolar organic compound which iselectrochemically stable.

Further, it is another object to provide a light-emitting element and alight-emitting device having low driving voltage and power consumptionby using the bipolar organic compound of the present invention. Inaddition, it is another object to provide a light-emitting element and alight-emitting device having a long lifetime by using the bipolarorganic compound of the present invention.

It is still another object to provide a long-life electronic device withlow power consumption and high thermal stability by using the bipolarorganic compound of the present invention.

One feature of the present invention is a quinoxaline derivativerepresented by a general formula (1).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms; and α representsan arylene group having 6 to 25 carbon atoms. A represents a substituentrepresented by any of general formulas (1-1) to (1-3). In the generalformulas (1-1) to (1-3), β represents an arylene group having 6 to 25carbon atoms; Ar³ and Ar⁴ each represent an aryl group having 6 to 25carbon atoms; Ar⁵ represents an aryl group having 6 to 25 carbon atoms;R³¹ represents any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms; γ representsan arylene group having 6 to 25 carbon atoms; and R⁴¹ and R⁴² eachrepresent any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (2).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms; and a representsan arylene group having 6 to 25 carbon atoms. A represents a substituentrepresented by any of general formulas (2-1) to (2-3). In the generalformulas (2-1) to (2-3), R¹¹ to R²⁴ each represent any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 15 carbon atoms; R³¹ represents any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R³² to R³⁶ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (3).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; R⁶ to R¹⁰each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 15 carbon atoms; and arepresents an arylene group having 6 to 25 carbon atoms. A represents asubstituent represented by any of general formulas (3-1) to (3-3). Inthe general formulas (3-1) to (3-3), R¹¹ to R²⁴ each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (4).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; and R⁶ toR¹⁰ each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 15 carbon atoms. A representsa substituent represented by any of general formulas (4-1) to (4-3). Inthe general formulas (4-1) to (4-3), R¹¹ to R²⁴ each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (5).

wherein R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; and R⁶ toR¹⁰ each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 15 carbon atoms. A representsa substituent represented by any of general formulas (5-1) to (5-3). Inthe general formulas (5-1) to (5-3), R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; and R⁴¹ and R⁴² each represent any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (6).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; Ar¹ represents an aryl group having 6 to 25 carbon atoms; and arepresents an arylene group having 6 to 25 carbon atoms. A represents asubstituent represented by any of general formulas (6-1) to (6-3). Inthe general formulas (6-1) to (6-3), β represents an arylene grouphaving 6 to 25 carbon atoms; Ar³ and Ar⁴ each represent an aryl grouphaving 6 to 25 carbon atoms; Ar⁵ represents an aryl group having 6 to 25carbon atoms; R³¹ represents any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; γ represents an arylene group having 6 to 25 carbon atoms; andR⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (7).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; and Ar¹ represents an aryl group having 6 to 25 carbon atoms; anda represents an arylene group having 6 to 25 carbon atoms. A representsa substituent represented by any of general formulas (7-1) to (7-3). Inthe general formulas (7-1) to (7-3), R¹¹ to R²⁴ each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (8).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms; and α represents an arylene group having 6 to 25 carbon atoms. Arepresents a substituent represented by any of general formulas (8-1) to(8-3). In the general formulas (8-1) to (8-3), R¹¹ to R²⁴ each representany of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (9).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; and R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms. A represents a substituent represented by any of general formulas(9-1) to (9-3). In the general formulas (9-1) to (9-3), R¹¹ to R²⁴ eachrepresent any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 15 carbon atoms; R³¹ represents anyof a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 25 carbon atoms; R³² to R³⁶ each represent any ofa hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R⁴¹ and R⁴² each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 25 carbon atoms; and R⁴³ to R⁴⁶ each represent any ofa hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms.

Another feature of the present invention is a quinoxaline derivativerepresented by a general formula (10).

wherein R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms. A represents a substituent represented by any of general formulas(10-1) to (10-3). In the general formulas (10-1) to (10-3), R³¹represents any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms; and R⁴¹ and R⁴²each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms.

Another feature of the present invention is a light-emitting elementusing the quinoxaline derivative, specifically, a light-emitting elementhaving the above-described quinoxaline derivative between a pair ofelectrodes.

Another feature of the present invention is a light-emitting elementhaving a light emitting layer between a pair of electrodes, where thelight emitting layer has the above-described quinoxaline derivative.

Another feature of the present invention is a light-emitting elementhaving a light emitting layer between a pair of electrodes, where thelight emitting layer has the above-described quinoxaline derivative anda substance emitting fluorescence.

Another feature of the present invention is a light-emitting elementhaving a light emitting layer between a pair of electrodes, where thelight emitting layer has the above-described quinoxaline derivative anda substance emitting phosphorescence.

The light-emitting device of the present invention possesses alight-emitting element which has a layer including light-emittingsubstance between a pair of electrodes, and the layer including alight-emitting substance comprises the aforementioned quinoxalinederivative. The light-emitting device of the present invention has alsoa means for controlling light emission from the light-emitting element.The light-emitting device in this specification includes an imagedisplay device, a light-emitting device, or a light source (including alighting device). Further, the light-emitting device also includes amodule in which a connector such as an FPC (Flexible Printed Circuit), aTAB (Tape Automated Bonding) tape, or a TCP (Tape Carrier Package) isattached to a panel on which the light-emitting element is formed. Thelight-emitting device in this specification also includes a module inwhich a printed wiring board is provided at an end of a TAB tape or aTCP, and also includes a module in which an IC (Integrated Circuit) isdirectly mounted on the light-emitting element by a COG (Chip On Glass)method.

Further, an electronic device using the light-emitting element of thepresent invention in its display portion is also included in thecategory of the present invention. Therefore, the electronic device ofthe present invention has a display portion, and this display portion isequipped with the above-described light-emitting element and a means forcontrolling light emission of the light-emitting element.

The quinoxaline derivative of the present invention is bipolar andexcellent in both an electron transporting property and a holetransporting property. Further, the quinoxaline derivative of thepresent invention has a high glass transition temperature and excellentthermal stability. Furthermore, the quinoxaline derivative of thepresent invention is stable to electrochemical oxidation and reduction.

The quinoxaline derivative of the present invention is bipolar;therefore, by using the quinoxaline derivative of the present inventionin a light-emitting element, a light-emitting element and alight-emitting device having a low driving voltage and low powerconsumption can be obtained. In addition, a light-emitting element withhigh luminous efficiency can be obtained.

Further, the quinoxaline derivative of the present invention has a highglass transition temperature; therefore, by using the quinoxalinederivative of the present invention for a light-emitting element, alight-emitting element and a light-emitting device which have highthermal stability can be obtained.

The quinoxaline derivative of the present invention is stable toelectrochemical oxidation and reduction; therefore, by using thequinoxaline derivative of the present invention in a light-emittingelement, a light-emitting element and light-emitting device which have along lifetime can be obtained.

By using the quinoxaline derivative of the present invention, along-life electronic device with low power consumption and high thermalstability can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C are explanatory views of light-emitting elements of thepresent invention;

FIG. 2 is an explanatory view of a light-emitting element of the presentinvention;

FIG. 3 is an explanatory view of a light-emitting element of the presentinvention;

FIG. 4 is an explanatory view of an organic semiconductor element of thepresent invention;

FIGS. 5A and 5B are explanatory views of a light-emitting device of thepresent invention;

FIG. 6 is an explanatory view of a light-emitting device of the presentinvention;

FIGS. 7A to 7D are explanatory views of electronic devices of thepresent invention;

FIG. 8 is an explanatory view of an electronic device of the presentinvention;

FIG. 9 is an explanatory view of a lighting device of the presentinvention;

FIG. 10 is an explanatory view of a lighting device of the presentinvention;

FIGS. 11A and 11B are graphs each showing a ¹H NMR chart of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ);

FIG. 12 is a graph showing an absorption spectrum of a toluene solutionof 4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ);

FIG. 13 is a graph showing an emission spectrum of a thin film of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ);

FIGS. 14A and 14B are graphs each showing a ¹H NMR chart of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIG. 15 is a graph showing an absorption spectrum of a toluene solutionof4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIG. 16 is a graph showing an absorption spectrum of a thin film of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIG. 17 is a graph showing an emission spectrum of a toluene solution of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIG. 18 is a graph showing an emission spectrum of a thin film of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIG. 19 is a graph showing a result of CV measurement of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIG. 20 is a graph showing a result of CV measurement of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIGS. 21A and 21B are graphs each showing a ¹H NMR chart ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ);

FIG. 22 is a graph showing an absorption spectrum of a toluene solutionofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ);

FIG. 23 is a graph showing an absorption spectrum of a thin film ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ);

FIG. 24 is a graph showing an emission spectrum of a toluene solution ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ);

FIG. 25 is a graph showing an emission spectrum of a thin film ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ);

FIG. 26 is a graph showing a result of CV measurement ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ);

FIG. 27 is a graph showing a result of CV measurement ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ);

FIG. 28 is a graph showing a DSC chart of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ);

FIG. 29 is an explanatory view of a light-emitting element of examples;

FIG. 30 is a graph showing current density-luminance characteristics oflight-emitting elements fabricated in Example 4;

FIG. 31 is a graph showing voltage-luminance characteristics oflight-emitting elements fabricated in Example 4;

FIG. 32 is a graph showing luminance-current efficiency characteristicsof light-emitting elements fabricated in Example 4;

FIG. 33 is a graph showing voltage-current characteristics oflight-emitting elements fabricated in Example 4;

FIG. 34 is a graph showing luminance-power efficiency characteristics oflight-emitting elements fabricated in Example 4;

FIG. 35 is a graph showing emission spectra of light-emitting elementsfabricated in Example 4;

FIG. 36 is a graph showing time-dependence of normalized luminance oflight-emitting elements fabricated in Example 4;

FIG. 37 is a graph showing variation of driving voltage on time forlight-emitting elements fabricated in Example 4;

FIG. 38 is a graph showing current density-luminance characteristics oflight-emitting elements fabricated in Example 5;

FIG. 39 is a graph showing voltage-luminance characteristics oflight-emitting elements fabricated in Example 5;

FIG. 40 is a graph showing luminance-current efficiency characteristicsof light-emitting elements manufactured in Example 5;

FIG. 41 is a graph showing voltage-current characteristics oflight-emitting elements fabricated in Example 5;

FIG. 42 is a graph showing luminance-power efficiency characteristics oflight-emitting elements fabricated in Example 5;

FIG. 43 is a graph showing emission spectra of light-emitting elementsfabricated in Example 5;

FIG. 44 is a graph showing time-dependence of normalized luminance oflight-emitting elements fabricated in Example 5;

FIG. 45 is a graph showing variation of driving voltage on time forlight-emitting elements fabricated in Example 5;

FIG. 46 is a graph showing a current density-luminance characteristic ofa light-emitting element fabricated in Example 6;

FIG. 47 is a graph showing a voltage-luminance characteristic of alight-emitting element fabricated in Example 6;

FIG. 48 is a graph showing a luminance-current efficiency characteristicof a light-emitting element fabricated in Example 6;

FIG. 49 is a graph showing a voltage-current characteristic of alight-emitting element fabricated in Example 6;

FIG. 50 is a graph showing an emission spectrum of a light-emittingelement fabricated in Example 6;

FIGS. 51A and 51B are graphs each showing a ¹H NMR chart ofN-phenyl-(9-phenylcarbazol-3-yl)amine (abbreviation: PCA);

FIGS. 52A and 52B are graphs each showing a ¹H NMR chart of4-(carbazol-9-yl)-diphenylamine (abbreviation: YGA);

FIGS. 53A and 53B are graphs each showing a ¹H NMR chart of(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium (III);

FIG. 54 is a graph showing an absorption spectrum and an emissionspectrum of (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III);

FIGS. 55A and 55B are graphs each showing a ¹H NMR chart ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ);

FIG. 56 is a graph showing an absorption spectrum of a toluene solutionofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ);

FIG. 57 is a graph showing an emission spectrum of a toluene solution ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ);

FIGS. 58A and 58B are graphs each showing a ¹H NMR chart ofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ);

FIG. 59 is a graph showing an absorption spectrum of a toluene solutionofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ);

FIG. 60 is a graph showing an emission spectrum of a toluene solution ofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ);

FIG. 61 is a graph showing a current density-luminance characteristic ofa light-emitting element fabricated in Example 9;

FIG. 62 is a graph showing a voltage-luminance characteristic of alight-emitting element fabricated in Example 9;

FIG. 63 is a graph showing a luminance-current efficiency characteristicof a light-emitting element fabricated in Example 9;

FIG. 64 is a graph showing a voltage-current characteristic of alight-emitting element fabricated in Example 9;

FIG. 65 is a graph showing an emission spectrum of a light-emittingelement fabricated in Example 9;

FIG. 66 is a graph showing a current density-luminance characteristic ofa light-emitting element fabricated in Example 10;

FIG. 67 is a graph showing a voltage-luminance characteristic of alight-emitting element fabricated in Example 10;

FIG. 68 is a graph showing a luminance-current efficiency characteristicof a light-emitting element fabricated in Example 10;

FIG. 69 is a graph showing a voltage-current characteristic of alight-emitting element fabricated in Example 10;

FIG. 70 is a graph showing an emission spectrum of a light-emittingelement fabricated in Example 10;

FIG. 71 is a graph showing an absorption spectrum of a thin film of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ);

FIG. 72 is a graph showing an emission spectrum of a thin film of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ);

FIG. 73 is a graph showing an absorption spectrum of a thin film ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ);

FIG. 74 is a graph showing an emission spectrum of a thin film ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ);

FIG. 75 is a graph showing an absorption spectrum of a thin film ofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ); and

FIG. 76 is a graph showing an emission spectrum of a thin film ofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, Embodiment Modes of the present invention will be explainedwith reference to the accompanied drawings. However, the presentinvention is not limited to the explanation to be given below, and it isto be easily understood that various changes and modifications in modesand details thereof will be apparent to those skilled in the art withoutdeparting from the purpose and the scope of the present invention.Therefore, the present invention should not be interpreted as beinglimited to the description of the embodiment modes to be given below.

Embodiment Mode 1

In this embodiment mode, a quinoxaline derivative of the presentinvention will be explained.

A quinoxaline derivative of the present invention is a quinoxalinederivative represented by a general formula (1).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms; and a representsan arylene group having 6 to 25 carbon atoms. A represents a substituentrepresented by any of general formulas (1-1) to (1-3). In the generalformulas (1-1) to (1-3), P represents an arylene group having 6 to 25carbon atoms; Ar³ and Ar⁴ each represent an aryl group having 6 to 25carbon atoms; Ar⁵ represents an aryl group having 6 to 25 carbon atoms;R³¹ represents any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms; γ representsan arylene group having 6 to 25 carbon atoms; and R⁴¹ and R⁴² eachrepresent any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms.

Among the quinoxaline derivatives represented by the general formula(1), a quinoxaline derivative represented by a general formula (2) ispreferable.

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms; and a representsan arylene group having 6 to 25 carbon atoms. A represents a substituentrepresented by any of general formulas (2-1) to (2-3). In the generalformulas (2-1) to (2-3), R¹¹ to R²⁴ each represent any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 15 carbon atoms; R³¹ represents any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R³² to R³⁶ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms.

Among the quinoxaline derivatives represented by the general formula(1), a quinoxaline derivative represented by a general formula (3) ismore preferable.

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; R¹¹ to R¹⁰each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 15 carbon atoms; and arepresents an arylene group having 6 to 25 carbon atoms. A represents asubstituent represented by any of general formulas (3-1) to (3-3). Inthe general formulas (3-1) to (3-3), R¹¹ to R²⁴ each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Among the quinoxaline derivatives represented by the general formula(1), a quinoxaline derivative represented by a general formula (4) ismore preferable.

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; and R⁶ toR¹⁰ each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 15 carbon atoms. A representsa substituent represented by any of general formulas (4-1) to (4-3). Inthe general formulas (4-1) to (4-3), R¹¹ to R²⁴ each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Furthermore, among the quinoxaline derivatives represented by thegeneral formula (1), a quinoxaline derivative represented by a generalformula (5) is more preferable.

wherein R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; and R⁶ toR¹⁰ each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 15 carbon atoms. A representsa substituent represented by any of general formulas (5-1) to (5-3). Inthe general formulas (5-1) to (5-3), R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; and R⁴¹ and R⁴² each represent any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms.

A quinoxaline derivative of the present invention is a quinoxalinederivative represented by a general formula (6).

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; Ar¹ represents an aryl group having 6 to 25 carbon atoms; and arepresents an arylene group having 6 to 25 carbon atoms. A represents asubstituent represented by any of general formulas (6-1) to (6-3). Inthe general formulas (6-1) to (6-3), β represents an arylene grouphaving 6 to 25 carbon atoms; Ar³ and Ar⁴ each represent an aryl grouphaving 6 to 25 carbon atoms; Ar⁵ represents an aryl group having 6 to 25carbon atoms; R³¹ represents any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; γ represents an arylene group having 6 to 25 carbon atoms; andR⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms.

Among the quinoxaline derivatives represented by the general formula(6), a quinoxaline derivative represented by a general formula (7) ispreferable.

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; and Ar¹ represents an aryl group having 6 to 25 carbon atoms; anda represents an arylene group having 6 to 25 carbon atoms. A representsa substituent represented by any of general formulas (7-1) to (7-3). Inthe general formulas (7-1) to (7-3), R¹¹ to R²⁴ each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Among the quinoxaline derivatives represented by the general formula(6), a quinoxaline derivative represented by a general formula (8) ismore preferable.

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms; and α represents an arylene group having 6 to 25 carbon atoms. Arepresents a substituent represented by any of general formulas (8-1) to(8-3). In the general formulas (8-1) to (8-3), R¹¹ to R²⁴ each representany of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 15 carbon atoms; R³¹ represents any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R³² to R³⁶ each represent any of a hydrogen atom,an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to15 carbon atoms; R⁴¹ and R⁴² each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25carbon atoms; and R⁴³ to R⁴⁶ each represent any of a hydrogen atom, analkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 15carbon atoms.

Among the quinoxaline derivatives represented by the general formula(6), a quinoxaline derivative represented by a general formula (9) ismore preferable.

wherein R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; and R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms. A represents a substituent represented by any of general formulas(9-1) to (9-3). In the general formulas (9-1) to (9-3), R¹¹ to R²⁴ eachrepresent any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 15 carbon atoms; R³¹ represents anyof a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 25 carbon atoms; R³² to R³⁶ each represent any ofa hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms; R⁴¹ and R⁴² each represent any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 25 carbon atoms; and R⁴³ to R⁴⁶ each represent any ofa hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms.

Furthermore, among the quinoxaline derivatives represented by thegeneral formula (6), a quinoxaline derivative represented by a generalformula (10) is more preferable.

wherein R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 15 carbonatoms. A represents a substituent represented by any of general formulas(10-1) to (10-3). In the general formulas (10-1) to (10-3), R³¹represents any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms; and R⁴¹ and R⁴²each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms.

In the general formulas (1) to (3) and the general formulas (6) to (8),Ar¹, Ar³, Ar⁴, and Ar⁵ each represent an aryl group having 6 to 25carbon atoms. Specifically, substituents represented by structuralformulas (11-1) to (11-6) are exemplified.

In the general formulas (1) and (2) and the general formulas (6) and(7), α, β, and γ each represent an arylene group having 6 to 25 carbonatoms. Specifically, substituents represented by structural formulas(12-1) to (12-6) are exemplified.

In the general formulas (1) to (10) described above, R¹ to R⁵, R³¹, R⁴¹,and R⁴² each represent any of a hydrogen atom, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms.Specifically, substituents represented by structural formulas (13-1) to(13-10) are exemplified.

In the general formulas (2) to (5) and the general formulas (7) to (10),R⁶ to R¹⁰, R¹¹ to R²⁴, R³² to R³⁶, and R⁴³ to R⁴⁶ each represent any ofa hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 15 carbon atoms. Specifically, substituentsrepresented by structural formulas (14-1) to (14-9) are exemplified.

As a specific example of a quinoxaline derivative represented by thegeneral formulas (1) to (5), quinoxaline derivatives represented bystructural formulas (21) to (366) can be given. However, the presentinvention is not limited thereto.

Various reactions can be applied to synthesize the quinoxalinederivatives of the present invention. For example, a quinoxalinederivative can be prepared by the reactions shown in the followingreaction schemes (A-1), (A-2), and (B-1) to (B-6).

First, a compound including carbazole in a skeleton (compound A) isreacted with halogen or halides such as N-bromosuccinimide (NBS),N-iodosuccinimide (NIS), bromine (Br₂), potassium iodide (KI), or iodine(I₂) to synthesize a compound including 3-halogenated carbazole in askeleton (compound B), which is followed by the coupling reaction withan arylamine using a metal catalyst such as a palladium catalyst (Pdcatalyst) to give a compound C. In the synthetic scheme (A-1), a halogenelement (X) is preferably iodine or bromine. R³¹ represents any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 25 carbon atoms. Ar⁵ represents an aryl group having 6to 25 carbon atoms. Ar¹ represents an aryl group having 6 to 25 carbonatoms.

First, a compound including carbazole in a skeleton (compound D) isreacted with dihalide of an aromatic compound to synthesize a compoundincluding N-(halogenated aryl)carbazole in a skeleton (compound E), andthen N-(halogenated aryl)carbazole is subjected to coupling reactionwith arylamine using a metal catalyst such as palladium, giving acompound F. In the synthetic scheme (A-2), a halogen element (X¹ and X²)of dihalide of an aromatic compound is preferably iodine or bromine. X¹and X² may be the same or different from each other. R⁴¹ and R⁴² eachrepresent any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms. γ represents anarylene group having 6 to 25 carbon atoms. Ar¹ represents an aryl grouphaving 6 to 25 carbon atoms.

By the reaction shown in the synthetic scheme (B-1), the quinoxalinederivative of the present invention can be synthesized. In the syntheticscheme (B-1), R¹ to R⁴ each represent any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms; and a representsan arylene group having 6 to 25 carbon atoms. Further, β represents anarylene group having 6 to 25 carbon atoms, Ar³ and Ar⁴ each represent anaryl group having 6 to 26 carbon atoms. X¹ represents a halogen element.X¹ is preferably iodine or bromine.

By the reaction shown in the synthetic scheme (B-2), the quinoxalinederivative of the present invention can be synthesized from the compoundC prepared by the reaction illustrated in the synthetic scheme (A-1). Inthe synthetic scheme (B-2), R¹ to R⁴ each represent any of a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having6 to 25 carbon atoms; R⁵ represents any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; Ar¹ represents an aryl group having 6 to 25 carbon atoms; and arepresents an arylene group having 6 to 25 carbon atoms. Further, Ar⁵represents an aryl group having 6 to 25 carbon atoms; and R³¹ representsany of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or anaryl group having 6 to 25 carbon atoms. X¹ represents a halogen element.X¹ is preferably iodine or bromine.

By, the reaction shown in the synthetic scheme (B-3), the quinoxalinederivative of the present invention can be synthesized from the compoundF prepared in the synthetic scheme (A-2). In the synthetic scheme (B-3),R¹ to R⁴ each represent any of a hydrogen atom, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; R⁵represents any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms; Ar¹ represents anaryl group having 6 to 25 carbon atoms; and a represents an arylenegroup having 6 to 25 carbon atoms. Further, γ represents an arylenegroup having 6 to 25 carbon atoms; and R⁴¹ and R⁴² each represent any ofa hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 25 carbon atoms. X¹ represents a halogen element. X¹is preferably iodine or bromine.

By the reaction shown in the synthetic scheme (B-4), the quinoxalinederivative of the present invention can be synthesized. In the syntheticscheme (B-4), R¹ to R⁴ each represent any of a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; Ar¹ represents an aryl group having 6 to 25 carbon atoms; and αrepresents an arylene group having 6 to 25 carbon atoms. Further, βrepresents an arylene group having 6 to 25 carbon atoms, and Ar³ and Ar⁴each represent an aryl group having 6 to 26 carbon atoms. X¹ and X² eachrepresent a halogen element. X¹ and X² are preferably iodine or bromine.

By the reaction shown in the synthetic scheme (B-5), the quinoxalinederivative of the present invention can be synthesized from the compoundC prepared in the synthesis scheme (A-1). In the synthetic scheme (B-5),R¹ to R⁴ each represent any of a hydrogen atom, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms; and α representsan arylene group having 6 to 25 carbon atoms. Further, Ar⁵ represents anaryl group having 6 to 25 carbon atoms; and R³¹ represents any of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an arylgroup having 6 to 25 carbon atoms. X¹ and X² each represent a halogenelement. X¹ and X² are preferably iodine or bromine.

By the reaction shown in the synthetic scheme (B-6), the quinoxalinederivative of the present invention can be synthesized from the compoundF prepared in the synthetic scheme (A-2). In the synthetic scheme (B-6),R¹ to R⁴ each represent any of a hydrogen atom, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms; and a representsan arylene group having 6 to 25 carbon atoms. Further, γ represents anarylene group having 6 to 25 carbon atoms; and R⁴¹ and R⁴² eachrepresent any of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or an aryl group having 6 to 25 carbon atoms. X¹ and X² eachrepresent a halogen element. X¹ and X² are preferably iodine or bromine.

In the synthetic schemes (B-1) to (B-6), a compound represented by thegeneral formula (1-1a) corresponds to the case where A in the generalformula (1) is the general formula (1-1); a compound represented by thegeneral formula (1-2a) corresponds to the case where A in the generalformula (1) is the general formula (1-2); and a compound represented bythe general formula (1-3a) corresponds to the case where A in thegeneral formula (1) is the general formula (1-3). A compound representedby the general formula (6-1a) corresponds to the case where A in thegeneral formula (6) is the general formula (6-1); a compound representedby the general formula (6-2a) corresponds to the case where A in thegeneral formula (6) is the general formula (6-2); and a compoundrepresented by the general formula (6-3a) corresponds to the case whereA in the general formula (6) is the general formula (6-3).

The quinoxaline derivatives of the present invention are bipolar andexcellent in both an electron transporting property and a holetransporting property. Therefore, when the quinoxaline derivatives ofthe present invention are used for an electronics device, a goodelectric performance is attainable. Further, the quinoxaline derivativeof the present invention has a high glass transition temperature andexcellent in thermal stability; therefore, when the quinoxalinederivatives of the present invention are applied to an electronicsdevice, an electronics device having excellent thermal stability can beobtained. Furthermore, the quinoxaline derivative of the presentinvention is stable with respect to repeated electrochemicaloxidation-reduction cycles; therefore, when the quinoxaline derivativeof the present invention is used for an electronics device, a long-lifeelectronics device can be obtained.

Embodiment Mode 2

One mode of a light-emitting element using a quinoxaline derivative ofthe present invention will be explained below with reference to FIG. 1A.

A light-emitting element of the present invention has a plurality oflayers between a pair of electrodes. The plurality of layers arefabricated by stacking layers comprising a substance having a highcarrier injecting property and layers comprising substance having a highcarrier transporting property. These layers are stacked so that alight-emitting region is located in a region away from the electrodes,that is, recombination of carriers is performed in an area away from theelectrodes.

In this embodiment mode, a light-emitting element includes a firstelectrode 102, a first layer 103, a second layer 104, a third layer 105,and a fourth layer 106 which are sequentially stacked over the firstelectrode 102, and a second electrode 107 provided thereover. Followingdescription will be provided regarding the first electrode 102 as ananode and the second electrode 107 as a cathode.

A substrate 101 is used as a support of the light-emitting element. Forthe substrate 101, glass, plastic, or the like can be used, for example.Note that another material may be used as long as it functions as asupport in a manufacturing process of the light-emitting element.

As the first electrode 102, a metal, an alloy, a conductive compound, amixture thereof, or the like having a high work function (specifically,4.0 eV or more) is preferably used. Specifically, indium oxide-tin oxide(ITO: Indium Tin Oxide), indium oxide-tin oxide including silicon orsilicon oxide, indium oxide-zinc oxide (IZO: Indium Zinc Oxide), indiumoxide including tungsten oxide and zinc oxide (IWZO), or the like isgiven. Although these conductive metal oxide films are generally formedby sputtering, they may be formed by applying a sol-gel method or thelike. For example, a layer of indium oxide-zinc oxide (IZO) can beformed by a sputtering method using a target in which 1 to 20 wt % ofzinc oxide is added to indium oxide. A layer of indium oxide includingtungsten oxide and zinc oxide (IWZO) can be formed by a sputteringmethod using a target in which 0.5 to 5 wt % of tungsten oxide and 0.1to 1 wt % of zinc oxide are included in indium oxide. In addition, gold(Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr),molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), anitride of a metal (such as titanium nitride: TiN), or the like can beemployed.

The first layer 103 is a layer including a substance having a high holeinjection property. Molybdenum oxide (MoOx), vanadium oxide (VOx),ruthenium oxide (RuOx), tungsten oxide (WOx), manganese oxide (MnOx), orthe like can be used. Alternatively, the first layer 103 can be formedusing phthalocyanine-based compound such as phthalocyanine(abbreviation: H₂Pc) or copper phthalocyanine (CuPc), or a highmolecular compound such as poly(ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS), or the like.

Alternatively, a composite material formed by compositing an organiccompound with an inorganic compound can be used for the first layer 103.In particular, a composite of an organic compound with an inorganiccompound which has an electron accepting property with respect to theorganic compound possesses an excellent hole injecting property and holetransporting property. This is because electron transfer between theorganic compound and the inorganic compound occurs, increasing carrierdensity.

In a case of using a composite formed by compositing an organic compoundwith an inorganic compound for the first layer 103, the first layer 103can perform an ohmic contact with the first electrode 102; therefore, amaterial of the first electrode can be selected regardless of workfunction.

As the inorganic compound used for the composite, transition metal oxideis preferred. Especially, an oxide of metals ranging from Groups 4 to 8in the periodic table is preferred. Namely, it is preferable to usevanadium oxide, niobium oxide, tantalum oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide,because of their high electron accepting abilities. Above all,molybdenum oxide is particularly preferable because it is stable in air,has a low hygroscopicity and is easily treated.

As the organic compound of the composite, various compounds such as anaromatic amine compound, a carbazole derivative, an aromatichydrocarbon, and a high molecular weight compound (such as oligomer,dendrimer, or polymer) can be used. The organic compound preferably usedfor the composite is an organic compound having a high hole transportingproperty. Specifically, a substance having a hole mobility of greaterthan or equal to 10⁻⁶ cm²/Vs is preferably used. However, othermaterials can also be used as long as the hole transporting property ishigher than the electron transporting property. The organic compoundswhich can be used for the composite will be specifically shown below.

For example, the followings can be given as the aromatic amine compound:N,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine (abbreviation:DTDPPA); 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl(abbreviation: DPAB);4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD);1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B); and the like.

As the carbazole derivatives which can be used for the compositematerial, the followings can be given specifically:3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2);3-[N-(1-naphtyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1); and the like.

Moreover, 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP);1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB);9-[4-(N-carbazolyl)]phenyl-10-phenylanthracene (abbreviation: CzPA);1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene; or the likecan be used.

As the aromatic hydrocarbon which can be used for the composite, thefollowings can be given for example:2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA);2-tert-butyl-9,10-di(1-naphthyl)anthracene;9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA);2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA);9,10-di(2-naphthyl)anthracene (abbreviation: DNA);9,10-diphenylanthracene (abbreviation: DPAnth); 2-tert-butylanthracene(abbreviation: t-BuAnth); 9,10-bis(4-methyl-1-naphthyl)anthracene(abbreviation: DMNA);2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene;9,10-bis[2-(1-naphthyl)phenyl]anthracene;2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene;2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene; 9,9′-bianthryl;10,10′-diphenyl-9,9′-bianthryl;10,10′-bis(2-phenylphenyl)-9,9′-bianthryl;10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl; anthracene;tetracene; rubrene; perylene; 2,5,8,11-tetra(tert-butyl)perylene; andthe like. Besides these compounds, pentacene, coronene, or the like canalso be used. In particular, the aromatic hydrocarbon, which has a holemobility of greater than or equal to 1×10⁻⁶ cm²/Vs and simultaneouslyhas 14 to 42 carbon atoms, is more preferable.

The aromatic hydrocarbon which can be used for the composite may have avinyl group. As the aromatic hydrocarbon having a vinyl group, thefollowings are given for example: 4,4′-bis(2,2-diphenylvinyl)biphenyl(abbreviation: DPVBi); 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene(abbreviation: DPVPA); and the like.

Moreover, a high molecular weight compound such aspoly(N-vinylcarbazole) (abbreviation: PVK) orpoly(4-vinyltriphenylamine) (abbreviation: PVTPA) can also be used.

As a substance forming the second layer 104, a substance having a highhole transporting property, specifically, an aromatic amine compound(that is, a compound having a benzene ring-nitrogen bond) is preferable.A material that is widely used includes derivatives of4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl such as4,4′-bis[N-(1-napthyl)-N-phenylamino]biphenyl (hereinafter referred toas NPB), and star burst aromatic amine compounds such as4,4′,4″-tris(N,N-diphenyl-amino)triphenylamine, and4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine. Thesematerials described here are substances each having a hole mobility ofgreater than or equal to 10⁻⁶ cm²/Vs. However, other materials may alsobe used as long as the hole transporting property thereof are higherthan the electron transporting property. The second layer 104 is notlimited to a single layer, and two or more layers including theaforementioned compounds may be stacked.

The third layer 105 is a layer including a light-emitting substance. Inthis embodiment mode, the third layer 105 includes the quinoxalinederivative of the present invention described in Embodiment Mode 1. Thequinoxaline derivative of the present invention can preferably beapplied to a light-emitting element as a light-emitting substance sincethe quinoxaline derivative of the present invention exhibits emission ofblue to blue green light.

As the fourth layer 106, a substance having a high electron transportingproperty can be used. For example, a layer including a metal complex orthe like having a quinoline moiety or a benzoquinoline moiety such astris(8-quinolinolato)aluminum (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq) can be used. Alternatively, a metal complex or the like having anoxazole-based or thiazole-based ligand such asbis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂) orbis[2-(2-hydroxyphenyl)-benzothiazolato]zinc (abbreviation: Zn(BTZ)₂)can be used. Besides the metal complexes,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or the like can also be used. Thematerials described here mainly are substances each having an electronmobility of greater than or equal to 10⁻⁶ cm²/Vs. The electrontransporting layer may be formed using other materials as long as thematerials have higher electron transporting property than holetransporting property. Furthermore, the electron transporting layer isnot limited to a single layer, and two or more layers comprising theaforementioned materials may be stacked.

As a substance forming the second electrode 107, a metal, an alloy, aconductive compound, a mixture thereof, or the like having a low workfunction (specifically, 3.8 eV or less) is preferably used. As aspecific example of such a cathode material, an element belonging toGroup 1 or Group 2 in the periodic table, that is, an alkali metal suchas lithium (Li) or cesium (Cs), an alkaline earth metal such asmagnesium (Mg), calcium (Ca), or strontium (Sr), an alloy includingthese metals (such as an Mg—Ag alloy or an Al—Li alloy), a rare earthmetal such as europium (Eu) or ytterbium (Yb), an alloy including theserare earth metals, or the like is given. However, by introducing alayer, which has a function to promote electron injection, between thesecond electrode 107 and the fourth layer 106, various conductivematerials such as Al, Ag, ITO, or ITO including silicon can be used asthe second electrode 107 regardless of the magnitude of the workfunction.

As the layer having a function to promote electron injection, an alkalimetal compound or an alkaline earth metal compound such as lithiumfluoride (LiF), cesium fluoride (CsF), or calcium fluoride (CaF₂) can beused. Furthermore, a layer, in which a substance having an electrontransporting property is combined with an alkali metal or an alkalineearth metal, can be employed. For instance, Alq including magnesium (Mg)can be used. It is more preferable to use the layer, in which asubstance having an electron transporting property is combined with analkali metal or an alkaline earth metal, since electron injection fromthe second electrode 107 efficiently proceeds.

Various methods can be applied for fabricating the first layer 103, thesecond layer 104, the third layer 105, and the fourth layer 106. Forexample, a vapor deposition method, an ink-jet method, a spin coatingmethod, or the like may be used. Furthermore, each electrode or eachlayer may be formed by a different film formation method.

A current flows between the first electrode 102 and the second electrode107 by applying voltage to the light-emitting element having theaforementioned device structure. Holes and electrons are recombined inthe third layer 105 which includes a substance having a highlight-emitting ability. That is, the light-emitting element of thepresent invention has a structure in which a light-emitting region isproduced in the third layer 105.

Light emission is extracted outside through one or both of the firstelectrode 102 and the second electrode 107. Therefore, one or both ofthe first electrode 102 and the second electrode 107 is/are formed usinga substance having a light transmitting property. In a case where onlythe first electrode 102 is prepared using a substance having a lighttransmitting property, as shown in FIG. 1A, light is extracted from asubstrate side through the first electrode 102. Alternatively, in a casewhere only the second electrode 107 is formed using a substance having alight transmitting property, as shown in FIG. 1B, light is extractedfrom the side opposite to the substrate through the second electrode107. In a case where each of the first electrode 102 and the secondelectrode 107 are formed using a substance having a light transmittingproperty, as shown in FIG. 1C, light is extracted from both of thesubstrate side and the side opposite to the substrate through the firstelectrode 102 and the second electrode 107, respectively.

A structure of a layer provided between the first electrode 102 and thesecond electrode 107 is not limited to the above-described structure.Another structure may be used as long as the light-emitting region, inwhich holes and electrons are recombined, is located away from the firstelectrode 102 and the second electrode 107. By using such a devicestructure, quenching of the emission can be effectively suppressed sincethe quenching phenomenon readily occurs when the light-emitting regionis close to an electrode.

In other words, a stacked structure of the layer is not strictlylimited. A substance having a high electron transporting property, asubstance having a high hole transporting property, a substance having ahigh electron injecting property, a substance having a high holeinjecting property, a bipolar substance (substance having both a highelectron transporting property and high hole transporting property), ahole blocking material, or the like may be freely combined with thequinoxaline derivative which is disclosed in the present invention.

A light-emitting element shown in FIG. 2 has a structure in which afirst layer 303 comprising a substance with a high electron transportingproperty, a second layer 304 including a light emitting substance, athird layer 305 comprising a substance with a high hole transportingproperty, a fourth layer 306 comprising a substance with a high holeinjecting property, and a second electrode 307 serving as an anode aresequentially stacked over a first electrode 302 which works as acathode. Reference numeral 301 denotes a substrate.

In this embodiment mode, the light-emitting element is fabricated over asubstrate made of glass, plastic, or the like. By fabricating aplurality of light-emitting elements over one substrate, a passive typelight-emitting device can be manufactured. Alternatively, for example, athin film transistor (TFT) may be formed over a substrate made of glass,plastic, or the like, and the light-emitting elements may be fabricatedover an electrode electrically connected to the TFT. By this process, anactive matrix light-emitting device can be manufactured, in whichdriving of the light-emitting element is controlled by a TFT. Astructure of the TFT is not strictly limited, and may be a staggered TFTor an inverted staggered TFT. Crystallinity of a semiconductor used forthe TFT is also not limited, and an amorphous semiconductor or acrystalline semiconductor may be used. In addition, a circuit fordriving formed over a TFT substrate may be constructed using an N-typeTFT and a P-type TFT, or may be constructed using any one of an N-typeTFT and a P-type TFT.

Since the quinoxaline derivative of the present invention is bipolar andis a material having a light-emitting property. Therefore, as describedin this embodiment mode, the quinoxaline derivative of the presentinvention can be used as a light emitting layer without including otherlight-emitting substances.

Further, since the quinoxaline derivative of the present invention isbipolar, the light-emitting region is not readily localized at aninterface of the stacked layers. Hence, it is possible to provide ahigh-performance light-emitting element which shows almost no changes inemission spectrum and luminous efficiency, resulting from the exciplexformation, during operation. In addition, a light-emitting element withhigh luminous efficiency can be obtained.

Microcrystalline components are hardly generated in a layer formed usingthe quinoxaline derivatives of the present invention, which allowsformation of a layer with a high quality. Therefore, a light-emittingelement with few defects that result from the dielectric breakdown dueto electric field concentration can be manufactured.

The quinoxaline derivative of the present invention is a material whichis bipolar and excellent in a carrier transporting property (an electrontransporting property and a hole transporting property); therefore, byusing the quinoxaline derivative for a light-emitting element, aoperation voltage of the light-emitting element can be reduced, leadingto reduction in power consumption.

Further, the quinoxaline derivative of the present invention has a highglass transition temperature; therefore, by using the quinoxalinederivative of the present invention, a light-emitting element havinghigh thermal stability can be obtained.

Further, the quinoxaline derivative of the present invention is stablewith respect to repeated oxidation and reduction performed alternately.That is, the quinoxaline derivative is electrochemically stable.Therefore, by using the quinoxaline derivative of the present inventionin a light-emitting element, a long-life light-emitting element can beobtained.

Embodiment Mode 3

In this embodiment mode, a light-emitting element having a differentstructure from that described in Embodiment Mode 2 will be explained.

The third layer 105, described in Embodiment Mode 2, can be formed bydispersing the quinoxaline derivative of the present invention inanother substance, by which light emission can be obtained from thequinoxaline derivative of the present invention. Since the quinoxalinederivative of the present invention exhibits emission of blue to bluegreen light, a blue to blue green emissive light-emitting element can beobtained.

Here, various materials can be used as a substance in which thequinoxaline derivative of the present invention is dispersed. Inaddition to the substance having a high hole transporting property andthe substance having a high electron transporting property, which aredescribed in Embodiment Mode 2, 4,4′-bis(N-carbazolyl)-biphenyl(abbreviation: CBP),2,2′,2″-(1,3,5-benzenetri-yl)-tris[1-phenyl-1H-benzimidazole](abbreviation: TPBI), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), andthe like are given.

The quinoxaline derivative of the present invention is a material whichis bipolar and excellent in a carrier transporting property (an electrontransporting property and a hole transporting property); therefore, byusing the quinoxaline derivative of the present invention for alight-emitting element, a driving voltage of the light-emitting elementcan be reduced, leading to reduction in power consumption.

Further, the quinoxaline derivative of the present invention has a highglass transition temperature; therefore, by using the quinoxalinederivative of the present invention, a light-emitting element havinghigh thermal stability can be obtained.

Further, the quinoxaline derivative of the present invention is stablewith respect to repeated oxidation and reduction performed alternately.That is, the quinoxaline derivative is electrochemically stable.Therefore, by using the quinoxaline derivative of the present inventionto a light-emitting element, a long-life light-emitting element can beobtained.

It is to be noted that the structure described in Embodiment Mode 2 canbe appropriately used for layers other than the third layer 105.

Embodiment Mode 4

In this embodiment mode, a light-emitting element having a differentstructure from those described in Embodiment Modes 2 and 3 will beexplained.

The third layer 105, described in Embodiment Mode 2, can be formed bydispersing a light-emitting substance in the quinoxaline derivative ofthe present invention, whereby light emission from the light-emittingsubstance can be obtained.

The quinoxaline derivative of the present invention possessesbipolarity. Furthermore, microcrystalline components are hardlygenerated in a layer formed using the quinoxaline derivatives of thepresent invention, which allows formation of the layer with a highquality. Therefore, the quinoxaline derivative of the present inventioncan be preferably used as a material in which another light-emittingsubstance is dispersed.

In a case where the quinoxaline derivative of the present invention isused as a material in which another light-emitting substance isdispersed, an emission color originating from the light-emittingsubstance can be obtained. Further, it is also possible to obtainemission that which is mixed of the emission color originating from thequinoxaline derivative of the present invention and from thelight-emitting substance dispersed in the quinoxaline derivative.

Here, various materials can be used as a light-emitting substancedispersed in the quinoxaline derivative of the present invention.Specifically, a substance emitting fluorescence such as4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran(abbreviation: DCM1),4-(dicyanomethylene)-2-methyl-6-(julolidine-4-yl-vinyl)-4H-pyran(abbreviation: DCM2), N,N-dimethylquinacridone (abbreviation: DMQd),9,10-diphenylanthracene (abbreviation: DPA); 5,12-diphenyltetracene(abbreviation: DPT), coumarin 6, perylene, or rubrene can be used.Further, a substance emitting phosphorescence such asbis(2-phenylbenzothiazolato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: Ir(bt)₂(acac)),tris(2-phenylquinolinato-N,C^(2′))iridium(III) (abbreviation: Ir(pq)₃),bis(2-phenylquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(pq)₂(acac)),bis[2-(2′-benzo[4,5-α]thienyl)pyridinato-N,C^(3′))iridium(III)acetylacetonate (abbreviation: Ir(btp)₂(acac)),bis(1-phenylisoquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(piq)₂(acac)),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)),2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II)(abbreviation: PtOEP), or the like can be used.

Since the quinoxaline derivative of the present invention is a materialwhich is bipolar and excellent in a carrier transporting property (anelectron transporting property and a hole transporting property), byusing the quinoxaline derivative of the present invention for alight-emitting element, a driving voltage of the light-emitting elementcan be reduced.

Further, since the quinoxaline derivative of the present invention isbipolar, the light-emitting region is not readily localized at aninterface of the stacked layers. Hence, it is possible to provide ahigh-performance light-emitting element which shows almost no changes inemission spectrum and in luminous efficiency, resulting from theexciplex formation.

Further, since the quinoxaline derivative of the present invention isbipolar, a light-emitting region is not readily localized at aninterface of stacked films. Therefore, in a case where a substanceemitting phosphorescence is used, T-T annihilation can be prevented.Accordingly, a light-emitting element with high luminous efficiency canbe obtained.

Further, the quinoxaline derivative of the present invention has a highglass transition temperature; therefore, by using the quinoxalinederivative of the present invention, a light-emitting element havinghigh thermal stability can be obtained.

Further, the quinoxaline derivative of the present invention is stablewith respect to repeated oxidation and reduction performed alternately.That is, the quinoxaline derivative is electrochemically stable.Therefore, by using the quinoxaline derivative of the present inventionfor a light-emitting element, a long-life light-emitting element can beobtained.

It is to be noted that the structure described in Embodiment Mode 2 canbe appropriately used for layers other than the third layer 105.

Embodiment Mode 5

In this embodiment mode, a mode of a light-emitting element having astructure in which a plurality of light-emitting units according to thepresent invention is stacked (hereinafter, referred to as a stack typeelement) will be explained with reference to FIG. 3. This light-emittingelement has a plurality of light-emitting units between a firstelectrode and a second electrode. A structure similar to that of thelayer including a light-emitting substrate described in Embodiment Mode2 can be used for the light-emitting unit. That is, the light-emittingelement described in Embodiment Mode 2 is a light-emitting elementhaving one light-emitting unit, while this embodiment demonstrates alight-emitting element having a plurality of light-emitting units.

In FIG. 3, a first light-emitting unit 511 and a second light-emittingunit 512 are stacked between a first electrode 501 and a secondelectrode 502. An electrode similar to that described in Embodiment Mode2 can be applied to the first electrode 501 and the second electrode502. The first light-emitting unit 511 and the second light-emittingunit 512 may have the same structure or different structures, and astructure similar to those described in Embodiment Modes 2 to 4 can beapplied.

A charge generation layer 513 includes a composite of an organiccompound with metal oxide. The composite of an organic compound withmetal oxide is the composite described in Embodiment Mode 2, andincludes an organic compound and metal oxide such as vanadium oxide,molybdenum oxide, or tungsten oxide. As the organic compound, variouscompounds such as an aromatic amine compound, a carbazole derivative,aromatic hydrocarbon, and a high molecular weight compound (oligomer,dendrimer, polymer, or the like) can be used. The compound having holemobility of greater than or equal to 1×10⁻⁶ cm²/Vs is preferably appliedas an organic compound. However, other substances may also be used aslong as the hole transporting property is higher than the electrontransporting property. The composite of an organic compound with metaloxide is superior in a carrier injecting property and a carriertransporting property, and hence, low-voltage driving and low-currentdriving can be realized.

It is to be noted that the charge generation layer 513 may be formedwith a combination of a composite of an organic compound with metaloxide and other materials. For example, the charge generation layer 513may be formed with a combination of a layer including the composite ofan organic compound with metal oxide and a layer including one compoundselected from electron donating substances with a compound having a highelectron transporting property. Further, the charge generation layer 513may be formed by combining a layer including the composite of an organiccompound with metal oxide and a transparent conductive film.

Any structure is acceptable as the charge generation layer 513interposed between the first light-emitting unit 511 and the secondlight-emitting unit 512 as long as electrons can be injected to alight-emitting unit on one side and holes can be injected to alight-emitting unit on the other side when a voltage is applied betweenthe first electrode 501 and the second electrode 502.

In this embodiment mode, the light-emitting element having twolight-emitting units is explained; however, the present invention can besimilarly applied to a light-emitting element in which three or morelight-emitting units are stacked. By arranging a plurality oflight-emitting units between a pair of electrodes in such a manner thatthe plurality of light-emitting units is partitioned with a chargegeneration layer, like the light-emitting element according to thisembodiment mode, a long-life element which can emit light with a highluminance at low current density can be realized.

This embodiment mode can be appropriately combined with anotherembodiment mode.

Embodiment Mode 6

In this embodiment mode, a mode in which a quinoxaline derivative of thepresent invention is used for an active layer of a vertical transistor(SIT) which is one kind of an organic semiconductor element, will beexemplified.

The element has a structure in which a thin active layer 1202 includingthe quinoxaline derivative of the present invention is interposedbetween a source electrode 1201 and a drain electrode 1203, and a gateelectrode 1204 is embedded in the active layer 1202, as shown in FIG. 4.The gate electrode 1204 is electrically connected to a means forapplying a gate voltage, and the source electrode 1201 and the drainelectrode 1203 are electrically connected to a means for controlling thevoltage between the source and drain electrodes.

In such an element structure, when a voltage is applied between thesource and the drain under the condition where a gate voltage is notapplied, a current flows, as observed in a light-emitting element (an ONstate). When a gate voltage is applied in this state, a depletion layeris generated in the periphery of the gate electrode 1204, whereby acurrent does not flow (an OFF state). With the aforementioned mechanism,the element operates as a transistor.

In a vertical transistor, a material which has both a carriertransporting property and an excellent film quality is required for anactive layer similarly to a light-emitting element. The quinoxalinederivative of the present invention is useful since it sufficientlymeets the requirement. Further, since the quinoxaline derivative of thepresent invention has a high glass transition temperature, an organicsemiconductor element having high thermal stability can be obtained.

Embodiment Mode 7

In this embodiment mode, a light-emitting device manufactured using aquinoxaline derivative of the present invention will be explained.

In this embodiment mode, a light-emitting device manufactured using thequinoxaline derivative of the present invention will be explained withreference to FIGS. 5A and 5B. It is to be noted that FIG. 5A is a topview showing a light-emitting device and FIG. 5B is a cross-sectionalview of FIG. 5A taken along lines A-A′ and B-B′. This light-emittingdevice includes a driver circuit portion (source side driver circuit)denoted by reference numeral 601; a pixel portion denoted by referencenumeral 602; and a driver circuit portion (gate side driver circuit)denoted by reference numeral 603, which are indicated by dotted lines.These portions control light emission of the light-emitting element.Reference numeral 604 denotes a sealing substrate; reference numeral 605denotes a sealing material; and a portion surrounded by the sealingmaterial 605 corresponds to a space 607.

A lead wiring 608 is a wiring for transmitting a signal to be inputtedto the source side driver circuit 601 and the gate side driver circuit603. The wiring 608 receives a video signal, a clock signal, a startsignal, a reset signal, and the like from an FPC (flexible printedcircuit) 609 that is an external input terminal. It is to be noted thatonly the FPC is shown here; however, the FPC may be provided with aprinted wiring board (PWB). The light-emitting device in thisspecification includes not only a light-emitting device itself but alsoa light-emitting device attached with an FPC or a PWB.

Subsequently, a cross-sectional structure will be explained withreference to FIG. 5B. The driver circuit portion and the pixel portionare formed over an element substrate 610. Here, the source side drivercircuit 601, which is the driver circuit portion, and one pixel in thepixel portion 602 are shown.

A CMOS circuit, which is a combination of an n-channel TFT 623 and ap-channel TFT 624, is formed as the source side driver circuit 601. Thedriver circuit may be formed using various CMOS circuits, PMOS circuits,or NMOS circuits. Although a driver integration type in which a drivercircuit is formed over a substrate is described in this embodiment mode,a driver circuit is not necessarily formed over a substrate and can beformed outside a substrate.

The pixel portion 602 has a plurality of pixels, each of which includesa switching TFT 611, a current control TFT 612, and a first electrode613 which is electrically connected to a drain of the current controlTFT 612. It is to be noted that an insulator 614 is formed to cover anend portion of the first electrode 613. Here, a positive photosensitiveacrylic resin film is used for the insulator 614.

The insulator 614 is formed so as to have a curved surface havingcurvature at an upper end portion or a lower end portion thereof inorder to make the coverage favorable. For example, in a case of usingpositive photosensitive acrylic resin as a material for the insulator614, the insulator 614 is preferably formed so as to have a curvedsurface with a curvature radius (0.2 μm to 3 μm) only at the upper endportion thereof. Either a negative type resin which becomes insoluble inan etchant by light irradiation or a positive type resin which becomessoluble in an etchant by light irradiation can be used for the insulator614.

A layer 616 including a light-emitting substance and a second electrode617 are formed over the first electrode 613. Here, a material having ahigh work function is preferably used as a material for the firstelectrode 613 serving as an anode. For example, the first electrode 613can be formed by using stacked layers of a titanium nitride film and afilm including aluminum as its main component; a three-layer structureof a titanium nitride film, a film including aluminum as its maincomponent, and another titanium nitride film; or the like as well as asingle-layer film such as an ITO film, an indium tin oxide filmincluding silicon, an indium oxide film including 2 to 20 wt % of zincoxide, a titanium nitride film, a chromium film, a tungsten film, a Znfilm, or a Pt film. When the first electrode 613 has a stackedstructure, it can have low resistance as a wiring and form a favorableohmic contact. Further, the first electrode 613 can function as ananode.

The layer 616 including a light-emitting substance is formed by variousmethods such as a vapor deposition method using a metal mask, an ink-jetmethod, and a spin coating method. The layer 616 including alight-emitting substance has the quinoxaline derivative of the presentinvention described in Embodiment Mode 1. Further, the layer 616including a light-emitting substance may be formed using anothermaterial such as a high molecular weight compound (including an oligomerand a dendrimer).

As a material used for the second electrode 617 which is formed over thelayer 616 including a light-emitting substance and serves as a cathode,a material having a low work function (Al, Mg, Li, Ca, or an alloy or asalt thereof such as MgAg, Mg—In, Al—Li, LiF, or CaF₂) is preferablyused. In a case where light generated in the layer 616 including alight-emitting substance is transmitted through the second electrode617, stacked layers of a metal thin film and a transparent conductivefilm (ITO, indium oxide including 2 to 20 wt % of zinc oxide, indium tinoxide including silicon, zinc oxide (ZnO), or the like) are preferablyused as the second electrode 617.

By attaching the sealing substrate 604 to the element substrate 610 withthe sealing material 605, a light-emitting element 618 is provided inthe space 607 surrounded by the element substrate 610, the sealingsubstrate 604, and the sealing material 605. It is to be noted that thespace 607 is filled with the sealing material 605 as well as an inertgas (nitrogen, argon, or the like).

It is to be noted that an epoxy-based resin is preferably used as thesealing material 605. It is preferred to use a material with lowpermeability of moisture and oxygen. As the sealing substrate 604, aplastic substrate formed using FRP (Fiberglass-Reinforced Plastics), PVF(polyvinyl fluoride), polyester, acrylic resin, or the like can be usedas well as a glass substrate or a quartz substrate.

By the method described above, a light-emitting device manufacturedusing the quinoxaline derivative of the present invention can beobtained.

Since the quinoxaline derivative described in Embodiment Mode 1 is usedfor the light-emitting device of the present invention, a highperformance light-emitting device having can be obtained. Specifically,a light-emitting device having high thermal stability can be obtained.

Further, since the quinoxaline derivative of the present invention iselectrochemically stable, a long-life light-emitting device can beobtained.

Furthermore, since the quinoxaline derivative of the present inventionis a material which is bipolar and excellent in a carrier transportingproperty (an electron transporting property and a hole transportingproperty), by using the quinoxaline derivative of the present invention,a driving voltage of the light-emitting element can be reduced and powerconsumption of the light-emitting device can be reduced. In particular,in a case of using a phosphorescent substance as a light-emittingsubstance, a light-emitting device with high emission efficiency and lowpower consumption can be obtained.

As described above, in this embodiment mode, an active matrixlight-emitting device in which operation of a light-emitting element iscontrolled by a transistor is explained. Alternatively, a passive typelight-emitting device in which a light-emitting element is drivenwithout providing an element for driving such as a transistor may alsobe used. FIG. 6 shows a perspective view of a passive typelight-emitting device which is fabricated by applying the presentinvention. In FIG. 6, a layer 955 including a light-emitting substanceis provided between an electrode 952 and an electrode 956 over asubstrate 951. An edge portion of the electrode 952 is covered with aninsulating layer 953. Then, a partition layer 954 is provided over theinsulating layer 953. A side wall of the partition layer 954 slopes sothat a distance between one side wall and the other side wall becomesnarrow toward a substrate surface. In other words, a cross section ofthe partition layer 954 in the direction of a short side is trapezoidal,and a base (a side facing in the same direction as a plane direction ofthe insulating layer 953 and in contact with the insulating layer 953)is shorter than an upper side (a side facing in the same direction asthe plane direction of the insulating layer 953 and not in contact withthe insulating layer 953). Fabrication of the partition layer 954 inthis manner allows patterning the electrode 956. The passive typelight-emitting device can also be driven with low power consumption whenit includes the light-emitting element of the present invention whichoperates at a low driving voltage.

Embodiment Mode 8

In this embodiment mode, an electronic device of the present inventionincluding the light-emitting device described in Embodiment Mode 7 willbe explained. The electronic device of the present invention includingthe quinoxaline derivative described in Embodiment Mode 1 has a displayportion which shows high thermal stability, a long lifetime, and lowpower consumption.

As an electronic device including a light-emitting element manufacturedusing the quinoxaline derivative of the present invention, a videocamera, a digital camera, a goggle type display, a navigation system, anaudio reproducing device (car audio component stereo, audio componentstereo, or the like), a computer, a game machine, a portable informationterminal (mobile computer, mobile phone, portable game machine,electronic book, or the like), and an image reproducing device providedwith a recording medium (specifically, a device capable of reproducing arecording medium such as a Digital Versatile Disc (DVD) and providedwith a display device that can display the image), and the like aregiven. Specific examples of these electronic devices are shown in FIGS.7A to 7D.

FIG. 7A shows a television device according to the present invention,which includes a housing 9101, a supporting base 9102, a display portion9103, a speaker portion 9104, a video input terminal 9105, and the like.In the television device, the display portion 9103 has light-emittingelements similar to those described in Embodiment Modes 2 to 5, whichare arranged in matrix. One feature of the light-emitting element isthat driving at a low voltage can be performed, the life is long, andthe heat resistance is high. The display portion 9103 which includes thelight-emitting elements has a similar feature. Therefore, in thetelevision device, image quality is hardly deteriorated and low powerconsumption is achieved. With such a feature, deterioration compensationfunction circuits and power supply circuits can be significantly reducedor downsized in the television device; therefore, small sized andlightweight housing 9101 and supporting base 9102 can be achieved. Inthe television device according to the present invention, low powerconsumption, high image quality, and small size and lightweight areachieved; therefore, a product which is suitable for living environmentcan be provided.

FIG. 7B shows a computer according to the present invention, whichincludes a main body 9201, a housing 9202, a display portion 9203, akeyboard 9204, an external connection port 9205, a pointing mouse 9206,and the like. In the computer, the display portion 9203 haslight-emitting elements similar to those described in Embodiment Modes 2to 5, which are arranged in matrix. One feature of the light-emittingelement is that driving at a low voltage can be performed, the life islong, and the heat resistance is high. The display portion 9203 whichincludes the light-emitting elements has a similar feature. Therefore,in the computer, image quality is hardly deteriorated and lower powerconsumption is achieved. With such a feature, deterioration compensationfunction circuits and power supply circuits can be significantly reducedor downsized in the computer; therefore, small sized and lightweightmain body 9201 and housing 9202 can be achieved. In the computeraccording to the present invention, low power consumption, high imagequality, and small size and lightweight are achieved; therefore, aproduct which is suitable for environment can be provided.

FIG. 7C shows a mobile phone according to the present invention, whichincludes a main body 9401, a housing 9402, a display portion 9403, anaudio input portion 9404, an audio output portion 9405, an operation key9406, an external connection port 9407, an antenna 9408, and the like.In the mobile phone, a display portion 9403 has light-emitting elementssimilar to those described in Embodiment Modes 2 to 5, which arearranged in matrix. One feature of the light-emitting element is thatdriving at a low voltage can be performed, the life is long, and theheat resistance is high. The display portion 9403 which includes thelight-emitting elements has a similar feature. Therefore, in the mobilephone, image quality is hardly deteriorated and lower power consumptionis achieved. With such a feature, deterioration compensation functioncircuits and power supply circuits can be significantly reduced ordownsized in the mobile phone; therefore, small sized and lightweightmain body 9401 and housing 9402 can be achieved. In the mobile phoneaccording to the present invention, low power consumption, high imagequality, and a small size and lightweight are achieved; therefore, aproduction which is suitable for carrying can be provided.

FIG. 7D shows a camera according to the present invention, whichincludes a main body 9501, a display portion 9502, a housing 9503, anexternal connection port 9504, a remote control receiving portion 9505,an image receiving portion 9506, a battery 9507, an audio input portion9508, operation keys 9509, an eye piece portion 9510, and the like. Inthe camera, the display portion 9502 has light-emitting elements similarto those described in Embodiment Modes 2 to 5, which are arranged inmatrix. One feature of the light-emitting element is that driving at alow voltage can be performed, the life is long, and the heat resistanceis high. The display portion 9502 which includes the light-emittingelements has a similar feature. Therefore, in the camera, image qualityis hardly deteriorated and lower power consumption can be achieved. Withsuch a feature, deterioration compensation function circuits and powersupply circuits can be significantly reduced or downsized in the camera;therefore, a small sized and lightweight main body 9501 can be achieved.In the camera according to the present invention, low power consumption,high image quality, and small size and lightweight are achieved;therefore, a product which is suitable for carrying can be provided.

As described above, the applicable range of the light-emitting device ofthe present invention is so wide that the light-emitting device can beapplied to electronic devices in various fields. By using thequinoxaline derivative of the present invention, electronic deviceshaving display portions that show low power consumption, long lifetime,and high thermal stability can be provided.

The light-emitting device of the present invention can also be used as alighting device. One mode using the light-emitting element of thepresent invention as the lighting device will be explained withreference to FIG. 8.

FIG. 8 shows an example of a liquid crystal display device using thelight-emitting device of the present invention as a backlight. Theliquid crystal display device shown in FIG. 8 includes a housing 901, aliquid crystal layer 902, a backlight 903, and a housing 904, and theliquid crystal layer 902 is connected to a driver IC 905. Thelight-emitting device of the present invention is used for the backlight903, and current is supplied through a terminal 906.

By using the light-emitting device of the present invention as thebacklight of the liquid crystal display device, a backlight with reducedpower consumption can be obtained. The light-emitting device of thepresent invention is a lighting device with plane emission area, andenlargement of the emission area is readily performed, which allowsenlargement of the backlight and, simultaneously, manufacturing a liquidcrystal display device having a large display area. Furthermore, thelight-emitting device of the present invention has a thin shape andconsumes low power; therefore, reduction of the thickness and powerconsumption of a display device can also be achieved. Since thelight-emitting device of the present invention has a long lifetime andexcellent thermal stability, a liquid crystal display device using thelight-emitting device of the present invention also has a long lifetimeand an excellent thermal stability.

FIG. 9 representatively demonstrates an application of the presentinvention into a table lamp as a lighting device. A table lamp shown inFIG. 9 has a chassis 2001 and a light source 2002, and thelight-emitting device of the present invention is used as the lightsource 2002. The light-emitting device of the present invention can emitlight with high luminance; therefore, when detailed work is beingperformed, the area at hand where the work is being performed can bebrightly lighted up.

FIG. 10 exemplifies an application of the present invention into anindoor lighting device 3001 as a light-emitting device. Since thelight-emitting device of the present invention can possess a largeemission area, the light-emitting device of the present invention can beused as a lighting device having a large emission area. Further, thelight-emitting device of the present invention has a thin shape andconsumes low power; therefore, the light-emitting device of the presentinvention can be used as a lighting device having a thin shape andconsuming low power. A television device according to the presentinvention as explained in FIG. 7A is placed in a room in which thepresent invention is applied to the indoor lighting device 3001 as alight-emitting device. Thus, public broadcasting and movies can bewatched. In such a case, since both of the devices consume low power, apowerful image can be watched in a bright room without concern aboutelectricity charges.

EXAMPLE 1

In this example, a synthetic method of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ) that is a quinoxaline derivative of the presentinvention represented by a structural formula (159) will be specificallyshown.

[Step 1]

A synthetic method of 2-(4-bromophenyl)-3-phenylquinoxaline will beexplained.

(i) Synthesis of (4-bromophenyl)phenylacetylene

A synthetic scheme of (4-bromophenyl)phenylacetylene is shown in (C-1).

28.3 g (0.10 mol) of p-bromoiodobenzene, 10.2 g (0.10 mol) ofphenylacetylene, 701 mg (1 mmol) ofbis(triphenylphosphine)palladium(II)dichloride, and 190 mg (1 mmol) ofcopper (I) iodide were placed in a 1000-mL three-neck flask, andnitrogen substitution was carried out. Then, 350 mL of tetrahydrofuranand 18 mL of triethylamine were added thereto, and the mixture wasstirred at room temperature for 12 hours. After the reaction, thereaction mixture washed with a 3% hydrochloric acid aqueous solution,and the aqueous phase was extracted with ethyl acetate. The extractedsolution combined with the organic phase washed with brine and driedwith magnesium sulfate. The mixture was filtered through celite,florisil, and alumina, and a solid obtained by the concentration of thefiltrate was recrystallized with hexane to give 15 g of a solid that wasthe target substrate in the yield of 58%.

(ii) Synthesis of 1-(4-bromophenyl)-2-phenylethanedione

A synthetic scheme of 1-(4-bromophenyl)-2-phenylethanedione is shown in(C-2).

10.0 g (38.9 mmol) of (4-bromophenyl)phenylacetylene, 4.7 g (18.5 mmol)of iodine, and 100 mL of dimethyl sulfoxide were placed in a 300-mLthree-neck flask, and the mixture was stirred at 155° C. for 4 hours.After the reaction, the reaction solution was cooled, then the reactionsolution was put into a 1 wt % sodium sulfate aqueous solution. Theprecipitated solid was collected by suction filtration. The residue wasdissolved into ethanol, and the insoluble part was filtered off throughcelite. The filtrate was concentrated, and the obtained solid wasdissolved into ethyl acetate. The insoluble part was filtered off againby celite-filtration, and the filtrate was concentrated. A firstrecrystallization was performed on the obtained solid with ethyl acetateand hexane, giving 1.5 g of the target substrate as a solid. A secondrecrystallization was performed on the filtrate with acetone and hexane,giving 6.7 g of the target substrate as a solid. By the two-timerecrystallization, 8.2 g of the product was obtained in the yield of72%.

(iii) Synthetic of 2-(4-bromophenyl)-3-phenylquinoxaline

A synthesis scheme of 2-(4-bromophenyl)-3-phenylquinoxaline is shown in(C-3).

8.2 g (29 mmol) of 1-(4-bromophenyl)-2-phenylethanedione, 3.1 g (31mmol) of o-phenylenediamine, and 100 mL of ethanol were placed into a300-mL flask, and the mixture was refluxed for 2 hours. After thereaction, the precipitated solid was collected by suction filtration.The collected solid washed with ethanol and dried. 7.3 g of alight-yellow solid was obtained as the target substrate in 69% yield.

[Step 2]

A synthetic method of 4-(carbazol-9-yl)-diphenylamine (abbreviation:YGA) will be explained.

(i) Synthesis of N-(4-bromophenyl)carbazole

A synthetic scheme of N-(4-bromophenyl)carbazole is shown in (C-4).

First, a synthesis of N-(4-bromophenyl)carbazole will be explained. 56.3g (0.24 mol) of 1,4-dibromobenzene, 31.3 g (0.18 mol) of carbazole, 4.6g (0.024 mol) of copper iodide, 66.3 g (0.48 mol) of potassiumcarbonate, and 2.1 g (0.008 mol) of 18-crown-6-ether were placed into a300-mL three-neck flask, and nitrogen substitution was carried out.Then, 8 mL of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone(abbreviation: DMPU) was added thereto, and the mixture was stirred at180° C. for 6 hours. After the reaction mixture was cooled to roomtemperature, the precipitate was removed by suction filtration. Thefiltrate washed with a diluted hydrochloric acid, a saturated sodiumhydrogencarbonate aqueous solution and brine, and then dried withmagnesium sulfate. After the drying, the reaction mixture was filteredand the filtrate was concentrated. The obtained oily residue waspurified by silica gel column chromatography (hexane:ethyl acetate=9:1),and the obtained solid was recrystallized with chloroform/hexane toresult in 20.7 g of a light-brown plate-like crystal ofN-(4-bromophenyl)carbazole in the yield of 35%. This compound wasconfirmed by a nuclear magnetic resonance method (NMR) to beN-(4-bromophenyl)carbazole.

¹H NMR data of this compound is shown below.

¹H NMR (300 MHz, CDCl₃); δ=8.14 (d, J=7.8 Hz, 2H), δ=7.73 (d, J=8.7 Hz,2H), δ=7.46 (d, J=8.4 Hz, 2H), δ=7.42-7.26 (m, 6H).

(ii) Synthesis of 4-(carbazol-9-yl)-diphenylamine (Abbreviation: YGA)

A synthetic scheme of YGA is shown in (C-5).

5.4 g (17.0 mmol) of N-(4-bromophenyl)carbazole obtained in thesynthetic procedure (i), 1.8 mL (20.0 mmol) of aniline, 100 mg (0.17mmol) of bis(dibenzylideneacetone)palladium(0), and 3.9 g (40 mmol) ofsodium tert-butoxide were put into a 200-mL three-neck flask, andnitrogen substitution was carried out. Then, 0.1 mL oftri-tert-butylphosphine (10 wt % hexane solution) and 50 mL of toluenewere added thereto, and the mixture was stirred at 80° C. for 6 hours.The reaction mixture was filtered through florisil, celite, and alumina.The filtrate was washed with water and brine, and then dried withmagnesium sulfate. The reaction mixture was filtered, and the filtratewas concentrated to give oily substance. This substance was purified bysilica gel column chromatography (hexane:ethyl acetate=9:1), leading tothe formation of 4.1 g of 4-(carbazol-9-yl)-diphenylamine (abbreviation:YGA) in the yield of 73%. It was confirmed by a nuclear magneticresonance method (NMR) that this compound was4-(carbazol-9-yl)-diphenylamine (abbreviation: YGA).

¹H NMR data of this compound is shown below.

¹H NMR (300 MHz, DMSO-d₆); δ=8.47 (s, 1H), δ=8.22 (d, J=7.8 Hz, 2H),δ=7.44-7.16 (m, 14H), δ=6.92-6.87 (m, 1H).

FIGS. 52A and 52B each show a ¹H NMR chart, and FIG. 52B shows anexpanded chart of FIG. 52A in a range of 6.7 ppm to 8.6 ppm.

[Step 3]

Synthesis of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(Abbreviation: YGA1PQ)

A scheme for the preparation of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ) is shown in (C-6).

2.0 g (5.59 mmol) of 2-(4-bromophenyl)-3-phenylquinoxaline, 2.07 g (5.59mmol) of 4-(carbazol-9-yl)-diphenylamine (abbreviation: YGA), 0.161 g(0.279 mmol) of bis(dibenzylideneacetone)palladium(0), and 2.68 g (27.93mmol) of tert-butoxysodium were placed into a 100-mL three-neck flask,and nitrogen substitution was carried out. 30 mL of toluene and 0.57 g(0.279 mmol) of tri-tert-butylphosphine (10% hexane solution) were addedthereto, and the mixture was stirred at 80° C. for 6 hours. After thereaction, the mixture washed with water, and the water phase wasextracted with toluene. The organic phase was dried with magnesiumsulfate. After the drying, the residue that was obtained by filtrationfollowed by concentration was dissolved into toluene, and the solutionwas passed through celite, florisil, and alumina. The filtrate wasconcentrated, and the reside was recrystallized with chloroform,methanol, and hexane, giving 2.25 g of a yellow solid in the yield of65%. It was confirmed by a nuclear magnetic resonance method (NMR) thatthis compound was4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ).

¹H NMR data of this compound is shown below.

¹H NMR (CDCl₃, 300 MHz): δ=7.11-7.14 (m, 3H), 7.21-7.48 (m, 19H),7.59-7.62 (m, 2H), 7.75-7.78 (m, 2H), 8.13-8.20 (m, 4H).

FIGS. 11A and 11B each show a ¹H NMR chart, and FIG. 11B shows anexpanded chart of FIG. 11A in a range of 6.5 ppm to 8.5 ppm.

The decomposition temperature (T_(d)) of YGA1PQ measured by athermo-gravimetric/differential thermal analyzer (TG/DTA 320,manufactured by Seiko Instruments Inc.) was 424° C., which means thatYGA1PQ shows high thermal stability.

FIG. 12 shows an absorption spectrum of a toluene solution of YGA1PQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The solution was put into aquartz cell, and the absorption spectrum thereof, from which theabsorption spectrum of quartz was subtracted, is shown in FIG. 12. InFIG. 12, the horizontal axis indicates the wavelength (nm) and thevertical axis indicates the absorption intensity (arbitrary unit). Theabsorption was observed at around 396 nm in the case of the toluenesolution. FIG. 13 shows the emission spectrum and the excitationspectrum of the toluene solution (the excitation wavelength: 368 nm) ofYGA1PQ. In FIG. 13, the horizontal axis indicates the wavelength (nm)and the vertical axis indicates the emission intensity (arbitrary unit).The maximum emission wavelength was 486 nm (the excitation wavelength:368 nm) in the case of the toluene solution.

FIG. 71 shows an absorption spectrum of a thin film of YGA1PQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The thin film sample wasprepared by vapor deposition of substrate on a quartz substrate, and theabsorption spectrum thereof, from which the absorption spectrum of aquartz substrate was subtracted, is shown in FIG. 71. In FIG. 71, thehorizontal axis indicates the wavelength (nm) and the vertical axisindicates the absorption intensity (arbitrary unit). The absorption wasobserved at around 406 nm in the case of the thin film. FIG. 72 showsthe emission spectrum of a thin film (the excitation wavelength: 406 nm)of YGA1PQ. In FIG. 72, the horizontal axis indicates the wavelength (nm)and the vertical axis indicates the emission intensity (arbitrary unit).The maximum emission wavelength was 513 nm (the excitation wavelength:406 nm) in the case of the thin film.

The result of measuring the thin-film using a photoelectron spectrometer(AC-2, manufactured by Riken Keiki Co., Ltd.) under the atmosphereindicated that the HOMO level of YGA1PQ in the solid state is −5.45 eV.The Tauc plot of the absorption spectrum shown in FIG. 71 revealed thatthe absorption edge was 2.66 eV. Thus, the energy gap of YGA1PQ in thesolid state was estimated to be 2.66 eV, which means that the LUMO levelof YGA1PQ in the solid state is −2.79 eV.

An optimal molecular structure of YGA1PQ in the ground state wasestimated using a density functional theory (DFT) at the B3LYP/6-311 (d,p) level. The accuracy of calculation of the DFT is higher than that ofa Hartree-Fock (HF) method which neglects electron correlation. Inaddition, a calculation cost of the DFT is lower than that of a methodof perturbation (MP) which has the same level of accuracy of calculationas that of the DFT. Therefore, the DFT was employed in this calculation.The calculation was performed using a high performance computer (HPC)(Altix3700 DX, manufactured by SGI Japan, Ltd.). The singlet excitationenergy (energy gap) of YGA1PQ was calculated by applying atime-dependent density functional theory (TDDFT) at the B3LYP/6-311 (d,p) level to the molecular structure optimized by the DFT. The singletexcitation energy of YGA1PQ was calculated to be 2.77 eV. The tripletexcitation energy of YGA1PQ was calculated to be 2.43 eV. From theseresults, it can be concluded that the quinoxaline derivative of thepresent invention has high excitation energy, in particular, hightriplet excitation energy.

EXAMPLE 2

In this example, a synthetic method of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ) that is a quinoxaline derivative of the presentinvention represented by a structural formula (320) will be specificallyshown.

[Step 1]

Synthesis of 2,3-bis(4-bromophenyl)quinoxaline will be explained. Asynthetic scheme of 2,3-bis(4-bromophenyl)quinoxaline is shown in (D-1).

Under a nitrogen atmosphere, a chloroform solution (200 mL) of 30.0 g(81.5 mmol) of 4,4′-dibromobenzyl and 9.00 g (83.2 mmol) ofo-phenylenediamine was heated and refluxed at 80° C. for 3 hours. Afterthe reaction mixture was cooled to room temperature, the reactionsolution washed with water. The organic phase was separated, and thewater phase was extracted with chloroform. The chloroform phase washedwith brine together with the organic phase. The combined organic phasewas dried with magnesium sulfate, and the solution was filtered andconcentrated to give 33 g of 2,3-bis(4-bromophenyl)quinoxaline as awhite solid in the yield of 92%.

[Step 2]

A synthetic method of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ) will be explained. A synthetic scheme of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ) is shown in (D-2).

5.0 g (13.51 mmol) of 2,3-bis(4-bromophenyl)quinoxaline, 9.94 g (29.73mmol) of 4-(carbazol-9-yl)diphenylamine synthesized in Step 2 of Example1, 0.39 g (0.676 mol) of bis(dibenzylideneacetone)palladium(0), and 6.49g (67.57 mmol) of sodium tert-butoxide were put into a 300-mL three-neckflask, and nitrogen substitution was carried out. 80 mL of toluene and1.4 g (0.676 mmol) of tri-tert-butylphosphine (10% hexane solution) wereadded thereto, and the mixture was stirred at 80° C. for 6 hours. Afterthe reaction, the solution washed with water, and then, a water phasewas extracted with toluene. The organic phase was dried with magnesiumsulfate. After the drying, the residue that was obtained by filtrationand concentration of the organic phase was dissolved into toluene, andthe resulting solution was passed through celite, florisil, and alumina.The filtrate was concentrated, and the residue was recrystallized withchloroform/methanol/hexane to provide 9.34 g of a yellow solid in theyield of 73%. It was confirmed by a nuclear magnetic resonance method(NMR) that this compound was4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ).

¹H NMR data of this compound is shown below.

¹H NMR (CDCl₃, 300 MHz): δ=7.02-7.07 (m, 2H), 7.17-7.56 (m, 36H),7.74-7.77 (m, 2H), 8.12-8.19 (m, 6H).

FIGS. 14A and 14B each show a ¹H NMR chart, and FIG. 14B shows anexpanded chart of FIG. 14A in a range of 6.5 ppm to 8.5 ppm.

Further, the decomposition temperature (T_(d)) of YGAPQ measured by athermo-gravimetric/differential thermal analyzer (TG/DTA 320,manufactured by Seiko Instruments Inc.) was 450° C. Therefore, it wasproven that YGAPQ shows high thermal stability.

The glass transition temperature was measured using a differentialscanning calorimeter (Pyris 1 DSC, manufactured by PerkinElmer, Inc.).First, the sample was heated to 400° C. at a rate of 40° C./min to meltthe sample, and then cooled to room temperature at a rate of 40° C./min.Thereafter, the sample was heated again to 400° C. at a rate of 10°C./min, whereby a DSC chart of FIG. 28 was obtained. The temperature isshown in the X axis and a heat flow is shown in the Y axis in FIG. 28.An upwardness in the Y axis means endothermic. According to this chart,it was found that the glass transition temperature (T_(g)) of YGAPQ is150° C., and the melting point thereof is higher than or equal to 400°C. Thus, it was found that YGAPQ has a high glass transitiontemperature.

FIG. 15 shows an absorption spectrum of a toluene solution of YGAPQ.FIG. 16 shows an absorption spectrum of a thin film of YGAPQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The solution was put into aquartz cell and the thin film sample was prepared by vapor deposition ofYGAPQ on a quartz substrate. The absorption spectra thereof, from eachof which the absorption spectrum of quartz was subtracted, are shown inFIGS. 15 and 16. In FIGS. 15 and 16, the horizontal axis indicates thewavelength (nm) and the vertical axis indicates the absorption intensity(arbitrary unit). The absorption was observed at around 400 nm in thecase of the toluene solution, and at around 410 nm in the case of thethin film. FIG. 17 shows the emission spectrum and the excitationspectrum of the toluene solution (the excitation wavelength: 397 nm) ofYGAPQ. FIG. 18 shows the emission spectrum of the thin film (theexcitation wavelength: 410 nm) of YGAPQ. In FIGS. 17 and 18, thehorizontal axis indicates the wavelength (nm), and the vertical axisindicates the emission intensity (arbitrary unit). The maximum emissionwavelength was 488 nm (the excitation wavelength: 397 nm) in the case ofthe toluene solution, and at around 531 nm and 630 nm (the excitationwavelength: 410 nm) in the case of the thin film.

The result of measuring the thin-film using a photoelectron spectrometer(AC-2, manufactured by Riken Keiki Co., Ltd.) under the atmosphereindicated that the HOMO level of YGAPQ in the solid state is −5.42 eVThe optical energy gap evaluated by the results of the Tauc plot of theabsorption spectrum shown in FIG. 16 revealed that the energy gap ofYGAPQ in the solid state was 2.66 eV. This result means that the LUMOlevel of YGA1PQ in the solid state is −2.76 eV.

An optimal molecular structure of YGAPQ in a ground state was estimatedusing a density functional theory (DFT) at the B3LYP/6-311 (d, p) level.The accuracy of calculation of the DFT is higher than that of aHartree-Fock (HF) method which neglects electron correlation. Inaddition, a calculation cost of the DFT is lower than that of a methodof perturbation (MP) which has the same level of accuracy of calculationas that of the DFT. Therefore, the DFT was employed in this calculation.The calculation was performed using a high performance computer (HPC)(Altix3700 DX, manufactured by SGI Japan, Ltd.). The singlet excitationenergy (energy gap) of YGAPQ was calculated by applying a time-dependentdensity functional theory (TDDFT) at the B3LYP/6-311 (d, p) level to themolecular structure optimized by the DFT. The singlet excitation energyof YGAPQ was calculated to be 2.64 eV. The triplet excitation energy ofYGAPQ was calculated to be 2.38 eV. From these results, it can beconcluded that the quinoxaline derivative of the present invention is asubstance having high excitation energy, in particular, a substancehaving high triplet excitation energy.

Furthermore, the glass transition point (T_(g)) was measured using adifferential scanning calorimeter (Pyris 1 DSC, manufactured byPerkinElmer, Inc.). First, a sample was heated to 330° C. at a rate of40° C./min, and then cooled to room temperature at a rate of 40° C./min.Thereafter, the sample was heated to 330° C. at a rate of 10° C./min,and then cooled to room temperature at a rate of 40° C./min. As aresult, it was found that the glass transition temperature (T_(g)) ofYGAPQ is 150° C. Thus, it was found that YGAPQ has a high glasstransition temperature.

Subsequently, an oxidation profile and a reduction profile of YGAPQ weremeasured by the cyclic voltammetry (CV) technique. An electrochemicalanalyzer (ALS model 600A, manufactured by BAS Inc.) was used for themeasurement.

The solution for the CV measurement was prepared by using dehydratedN,N-dimethylformamide (DMF) (produced by Sigma-Aldrich Corp., 99.8%,catalog number: 22705-6) as a solvent, dissolving a supportingelectrolyte of tetra-n-butylammonium perchlorate (n-Bu₄NClO₄) (producedby Tokyo Chemical Industry Co., Ltd., catalog number: T0836) at aconcentration of 100 mmol/L, and dissolving the sample at aconcentration of 1 mmol/L. A platinum electrode (PTE platinum electrode,produced by BAS Inc.) was used as a working electrode, a platinumelectrode (Pt counter electrode (5 cm) for VC-3, produced by BAS Inc.)was used as an auxiliary electrode, and an Ag/Ag⁺ electrode (RE5non-aqueous solvent reference electrode, produced by BAS Inc.) was usedas a reference electrode. The CV measurement of YGAPQ was carried out atroom temperature.

The oxidation profile of YGAPQ was examined as follows. A scan, in whichthe potential of the working electrode with respect to the referenceelectrode was varied from 1 V to −0.21 V after changing it from −0.21 Vto 1 V, was regarded as one cycle, and measurement was performed for 100cycles. The reduction profile of YGAPQ was examined as follows. A scan,in which the potential of the working electrode with respect to thereference electrode was varied from −2.5 V to −0.3 V after changing itfrom −0.3 V to −2.5 V, was regarded as one cycle, and measurement wasperformed for 100 cycles. The scan rate of the CV measurement was set tobe 0.1 V/s.

FIG. 19 shows a result of CV measurement of YGAPQ in an oxidationregion, and FIG. 20 shows a result of CV measurement of YGAPQ in areduction region. In each of FIGS. 19 and 20, the horizontal axisindicates a potential (V) of the working electrode with respect to thereference electrode, and the vertical axis indicates a current value(μA) flowing between the working electrode and the auxiliary electrode.According to FIG. 19, currents for oxidation were observed at around 0.7V to 0.8 V (vs. Ag/Ag⁺). According to FIG. 20, currents indicatingreduction were observed at around −1.94 V (vs. Ag/Ag⁺).

EXAMPLE 3

In this example, a synthetic method ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ) that is a quinoxaline derivative of the presentinvention represented by a structural formula (271) will be specificallyshown.

Step 1

A synthetic method of N-phenyl-(9-phenylcarbazol-3-yl)amine(abbreviation: PCA) will be explained.

(i) Synthesis of 3-bromo-9-phenylcarbazole

A synthetic scheme of 3-bromo-9-phenylcarbazole is shown in (E-1).

24.3 g (100 mmol) of 9-phenylcarbazole was dissolved into 600 mL ofglacial acetic acid, and 17.8 g (100 mmol) of N-bromosuccinimide wasslowly added thereto, which was followed by stirring at room temperaturefor about 15 hours. This glacial acetic acid solution was dropped to 1 Lof ice water while being stirred, and a white solid which wasprecipitated was collected by suction filtration and washed with waterthree times. The solid was dissolved into 150 mL of diethyl ether, andthe solution washed with a saturated sodium hydrogencarbonate aqueoussolution and water. The organic layer was dried with magnesium sulfate.After filtration, the obtained filtrate was concentrated, and about 50mL of methanol was added thereto to homogeneously dissolve the residue.This solution was left at rest, and a white solid was precipitated. Thissolid was collected and dried, giving 28.4 g of a white powder of3-bromo-9-phenylcarbazole in the yield of 88%.

[Step 2] Synthesis of N-phenyl-(9-phenylcarbazol-3-yl)amine(Abbreviation: PCA)

A synthetic scheme of PCA is shown in (E-2).

19 g (60 mmol) of 3-bromo-9-phenylcarbazole, 340 mg (0.6 mmol) ofbis(dibenzylideneacetone)palladium(0), 1.6 g (3.0 mmol) of1,1-bis(diphenylphosphino)ferrocene, and 13 g (180 mmol) of sodiumtert-butoxide were put into a three-neck flask, and nitrogensubstitution was carried out. Then, 110 mL of dehydrated xylene and 7.0g (75 mmol) of aniline were added thereto. This mixture was heated andstirred at 90° C. for 7.5 hours under a nitrogen atmosphere. After thereaction was completed, about 500 mL of hot toluene was added to thereaction mixture, and the mixture was filtered through florisil,alumina, and celite. The obtained filtrate was concentrated, and hexaneand ethyl acetate was added thereto. Then, the mixture was irradiatedwith ultrasonic waves. The precipitated solid was collected by suctionfiltration, and the obtained solid was dried. 15 g of a cream-coloredpowder of N-phenyl-(9-phenylcarbazol-3-yl)amine (abbreviation: PCA) wasobtained in the yield of 75%. It was confirmed by a nuclear magneticresonance method (NMR) that this compound wasN-phenyl-(9-phenylcarbazol-3-yl)amine (abbreviation: PCA).

¹H NMR data of this compound is shown below.

¹H NMR (300 MHz, CDCl₃); 6.84 (t, J=6.9, 1H), 6.97 (d, J=7.8, 2H),7.20-7.61 (m, 13H), 7.90 (s, 1H), 8.04 (d, J=7.8, 1H).

FIG. 51A shows a ¹H NMR chart, and FIG. 51B shows an expanded chart ofFIG. 51A in a range of 5.0 ppm to 9.0 ppm.

[Step 3] Synthesis ofN,N-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(Abbreviation: PCAPQ)

A synthetic scheme ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ) is shown in (E-3).

1.79 g (4.08 mmol) of 2,3-bis(4-bromophenyl)quinoxaline, 3.0 g (8.97mmol) of N-phenyl-(9-phenylcarbazol-3-yl)amine (abbreviation: PCA),0.117 g (0.204 mol) of bis(dibenzylideneacetone)palladium(0), and 1.96 g(20.39 mmol) of sodium tert-butoxide were put into a 100-mL three-neckflask, and nitrogen substitution was carried out. 30 mL of toluene and0.5 g (0.245 mmol) of tri-tert-butylphosphine (10% hexane solution) wereadded thereto, and the mixture was stirred at 80° C. for 6 hours. Afterthe reaction, the mixture washed with water, and then, the water phasewas extracted with toluene. The organic phase was dried with magnesiumsulfate. After the drying, the residue that was obtained by filtrationand concentration was dissolved into toluene, and the solution waspassed through celite, florisil, and alumina. The filtrate wasconcentrated and the resulting solid was recrystallized with ethylacetate/methanol, giving 2.60 g of a bright yellow solid that was thetarget product in the yield of 67%. It was confirmed by a nuclearmagnetic resonance method (NMR) that this compound wasN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ).

¹H NMR data of this compound is shown below.

¹H NMR (CDCl₃, 300 MHz): δ=6.96-7.01 (m, 2H), 7.06-7.59 (m, 36H),7.68-7.72 (m, 2H), 7.94-7.97 (m, 4H), 8.10-8.13 (m, 2H).

FIGS. 21A and 21B each show a ¹H NMR chart, and FIG. 21B shows anexpanded chart of FIG. 21A in a range of 6.5 ppm to 8.5 ppm.

The decomposition temperature (T_(d)) of PCAPQ measured by athermo-gravimetric/differential thermal analyzer (TG/DTA 320,manufactured by Seiko Instruments Inc.) was 477° C. Therefore, it wasconfirmed that PCAPQ shows high thermal stability

FIG. 22 shows an absorption spectrum of a toluene solution of PCAPQ.FIG. 23 shows an absorption spectrum of a thin film of PCAPQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The solution was put into aquartz cell, and the thin film sample was formed by vapor deposition ofPCAPQ on a quartz substrate. The absorption spectra thereof, from eachof which the absorption spectrum of quartz was subtracted, are shown inFIGS. 22 and 23. In FIGS. 22 and 23, the horizontal axis indicates thewavelength (nm) and the vertical axis indicates the absorption intensity(arbitrary unit). The absorption was observed at around 404 nm in thecase of the toluene solution, and at around 426 nm in the case of thethin film. FIG. 24 shows the emission spectrum and the excitationspectrum of the toluene solution (the excitation wavelength: 395 nm) ofPCAPQ. FIG. 25 shows the emission spectrum of a thin film (theexcitation wavelength: 426 nm) of PCAPQ. In FIGS. 24 and 25, thehorizontal axis indicates the wavelength (nm), and the vertical axisindicates the emission intensity (arbitrary unit). The maximum emissionwavelength was 508 nm (the excitation wavelength: 395 nm) in the case ofthe toluene solution and 538 nm (the excitation wavelength: 426 nm) inthe case of the thin film.

The result of measuring PCAPQ in a thin-film state using a photoelectronspectrometer (AC-2, manufactured by Riken Keiki Co., Ltd.) under theatmosphere showed that the HOMO level of PCAPQ is −5.29 eV. The opticalenergy gap evaluated by the results of the Tauc plot of the absorptionspectrum shown in FIG. 23 revealed that the energy gap of YGAPQ in thesolid state was 2.55 eV. This result means that the LUMO level of YGA1PQin the solid state is −2.74 eV.

An oxidation profile and a reduction profile of PCAPQ were measured bycyclic voltammetry (CV) technique. An electrochemical analyzer (ALSmodel 600A, manufactured by BAS Inc.) was used for the measurement.

The solution for the CV measurement was prepared by using dehydratedN,N-dimethylformamide (DMF) (produced by Sigma-Aldrich Corp., 99.8%,catalog number: 22705-6) as a solvent, dissolving a supportingelectrolyte of tetra-n-butylammonium perchlorate (n-Bu₄NClO₄) (producedby Tokyo Chemical Industry Co., Ltd., catalog number: T0836) at theconcentration of 100 mmol/L and dissolving the sample at theconcentration of 1 mmol/L. A platinum electrode (PTE platinum electrode,produced by BAS Inc.) was used as a working electrode, a platinumelectrode (Pt counter electrode (5 cm) for VC-3, produced by BAS Inc.)was used as an auxiliary electrode, and an Ag/Ag⁺ electrode (RE5non-aqueous solvent reference electrode, produced by BAS Inc.) was usedas a reference electrode. PCAPQ was measured at room temperature.

The oxidation profile of PCAPQ was examined as follows. A scan, in whicha potential of the working electrode with respect to the referenceelectrode was varied from 0.7 V to −0.26 V after changing it from −0.26V to 0.7 V, was regarded as one cycle, and measurement was performed for100 cycles. The reduction reaction characteristic of PCAPQ was examinedas follows. A scan, in which a potential of the working electrode withrespect to the reference electrode was varied from −2.4 V to −0.6 Vafter changing it from −0.6 V to −2.4 V, was regarded as one cycle, andmeasurement was performed for 100 cycles. The scan rate of the CVmeasurement was set to be 0.1 V/s.

FIG. 26 shows the result of CV measurement of PCAPQ in an oxidationregion and FIG. 27 shows the result of CV measurement of PCAPQ in areduction region. In each of FIGS. 26 and 27, the horizontal axisindicates a potential (V) of the working electrode with respect to thereference electrode, and the vertical axis indicates a current value(μA) flowing between the working electrode and the auxiliary electrode.According to FIG. 26, currents indicating oxidation were observed ataround 0.50 V (vs. Ag/Ag⁺). According to FIG. 27, currents indicatingreduction were observed at around −2.01 V (vs. Ag/Ag⁺).

FIGS. 26 and 27 show that a reversible peak was obtained in both theoxidation region and reduction region. Further, even when the oxidationor reduction was repeated for 100 times, the cyclic voltamogram hardlychanged. This means that PCAPQ is stable with respect to oxidation andreduction, that is, electrochemically stable.

EXAMPLE 4

In this example, a light-emitting element of the present invention willbe explained with reference to FIG. 29. A chemical formula of thematerial used in this example, Example 5, and Example 6 is shown below.

(Light-Emitting Element 1)

First, indium tin oxide including silicon oxide was formed over a glasssubstrate 2101 by a sputtering method, thereby forming a first electrode2102. It is to be noted that a thickness thereof was 110 nm and anelectrode area was 2 mm×2 mm.

Next, the substrate, over which the first electrode was formed, wasfixed to a substrate holder in a vacuum evaporation apparatus so thatthe side, on which the first electrode was formed, faced downward.Subsequently, after the pressure of the evaporation apparatus wasreduced to approximately 10⁻⁴ Pa, a layer 2103 including a composite ofan organic compound with an inorganic compound was formed on the firstelectrode 2102 by co-evaporation of NPB and molybdenum oxide (VI). Athickness thereof was adjusted to be 50 nm and a weight ratio of NPB tomolybdenum oxide (VI) was adjusted to be 4:1 (=NPB:molybdenum oxide). Itis to be noted that the co-evaporation method is an evaporation methodin which evaporation is performed simultaneously from a plurality ofevaporation sources in one evaporation chamber.

Next, 4,4′-bis[N-(1-napthyl)-N-phenylamino]biphenyl (abbreviation: NPB)was deposited at the thickness of 10 nm over the composite-includinglayer 2103 by the vapor deposition technique using resistance heatingsystem, leading to the formation of a hole transporting layer 2104.

Furthermore, a light emitting layer 2105 with a thickness of 30 nm wasformed on the hole transporting layer 2104 by co-evaporation of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ), represented by the structural formula (320), with(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: Ir(tppr)₂(acac)). Here, a weight ratio of YGAPQ toIr(tppr)₂(acac) was adjusted to be 1:0.05 (=YGAPQ:Ir(tppr)₂(acac)).

After that, bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(abbreviation: BAlq) was formed at a thickness of 10 nm on the lightemitting layer 2105 by the vapor deposition technique using resistanceheating system, thereby forming an electron transporting layer 2106.

Moreover, an electron injecting layer 2107 with a thickness of 50 nm wasformed on the electron transporting layer 2106 by co-evaporation oftris(8-quinolinolato)aluminum (abbreviation: Alq) with lithium. Here, aweight ratio of Alq to lithium was adjusted to be 1:0.01 (=Alq:lithium).

Finally, aluminum was formed at a thickness of 200 nm on the electroninjecting layer 2107 by the vapor deposition technique using resistanceheating system, thereby forming a second electrode 2108. Accordingly, alight-emitting element 1 was fabricated.

(Comparative Light-Emitting Element 2)

A light emitting layer 2105 with a thickness of 30 nm was formed byco-evaporation of 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP) with(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: Ir(tppr)₂(acac)). Here, a weight ratio of CBP toIr(tppr)₂(acac) was adjusted to be 1:0.05 (=CBP:Ir(tppr)₂(acac)). Thecomparative light-emitting element 2 was formed in a same manner as thatof the light-emitting element 1 other than the light emitting layer.

FIG. 30 shows current density-luminance characteristics of thelight-emitting element 1 and the comparative light-emitting element 2.FIG. 31 shows voltage-luminance characteristics. FIG. 32 showsluminance-current efficiency characteristics. FIG. 33 showsvoltage-current characteristics. FIG. 34 shows luminance-powerefficiency characteristics. FIG. 35 shows emission spectra when acurrent of 1 mA flows. FIG. 35 indicates that emission of thelight-emitting element 1 and the comparative light-emitting element 2 isthe emission from Ir(tppr)₂(acac).

In the light-emitting element 1, the CIE chromaticity coordinates atluminance of 980 cd/m² were (x, y)=(0.66, 0.34), and emission of redlight was obtained. Current efficiency at luminance of 980 cd/m² was 12cd/A, and external quantum efficiency was as high as 11%. Voltage atluminance of 980 cd/m² was 4.8 V, and current density was 8.3 mA/cm².The power efficiency was 7.7 lm/W which is an extremely high value.

On the other hand, in the comparative light-emitting element 2, the CIEchromaticity coordinates at luminance of 970 cd/m² were (x, y)=(0.64,0.35), and emission of red light was obtained. Current efficiency atluminance of 970 cd/m² was 11 cd/A, and external quantum efficiency was8.4%. Voltage at luminance of 970 cd/m² was 7.8 V; current density, 8.4mA/cm²; and power efficiency, 4.6 lm/W.

As evidenced by FIG. 32, the light-emitting element 1 and thecomparative light-emitting element 2 show almost the same currentefficiency. However, as shown in FIGS. 31 and 33, the light-emittingelement 1 can be driven at lower voltage than the comparativelight-emitting element 2. That is, a voltage required for obtaining acertain luminance is reduced. As a result, as shown in FIG. 34, powerefficiency is improved and power consumption is reduced in thelight-emitting element 1 compared with the comparative light-emittingelement 2. Therefore, the use of the quinoxaline derivative of thepresent invention allows the fabrication of a light-emitting elementhaving low driving voltage and low power consumption.

FIG. 36 shows time-dependence of normalized luminance of thelight-emitting element 1 and the comparative light-emitting element 2.FIG. 37 shows change of the driving voltage on time. The measurement wascarried out at an initial luminance of 1000 cd/m². FIG. 36 shows thatchange of luminance on time of the light-emitting element 1 is smallcompared with that of the comparative light-emitting element 2.

FIG. 37 shows that change of voltage on time of the light-emittingelement 1 is small compared with the comparative light-emitting element2. Accordingly, by using the quinoxaline derivative of the presentinvention, a long-life light-emitting element can be obtained.

EXAMPLE 5

In this example, a light-emitting element of the present invention willbe explained with reference to FIG. 29.

(Light-Emitting Element 3)

First, indium tin oxide including silicon oxide was formed over a glasssubstrate 2101 by a sputtering method, thereby forming a first electrode2102. It is to be noted that a thickness thereof was 110 nm and anelectrode area was 2 mm×2 mm.

Next, the substrate, over which the first electrode was formed, wasfixed to a substrate holder in a vacuum evaporation apparatus so thatthe side, on which the first electrode was formed, faced downward.Subsequently, a layer 2103 including a composite of an organic compoundwith an inorganic compound was formed on the first electrode 2102 byco-evaporation of NPB and molybdenum oxide (VI) after a pressure of theevaporation apparatus was reduced to approximately 10⁻⁴ Pa. A thicknessthereof was adjusted to be 50 nm and a weight ratio of NPB to molybdenumoxide (VI) was adjusted to be 4:1 (=NPB:molybdenum oxide). It is to benoted that the co-evaporation method is an evaporation method in whichevaporation is performed simultaneously from a plurality of evaporationsources in one evaporation chamber.

Next, 4,4′-bis[N-(1-napthyl)-N-phenylamino]biphenyl (abbreviation: NPB)was deposited at the thickness of 10 nm on the composite-including layer2103 by the vapor deposition technique using resistance heating system,leading to the formation of a hole transporting layer 2104.

Furthermore, a light emitting layer 2105 with a thickness of 30 nm wasformed on the hole transporting layer 2104 by co-evaporation of4,4′-(quinoxaline-2,3-diyl)bis{N-[4-(9-carbazolyl)phenyl]-N-phenylbenzeneamine}(abbreviation: YGAPQ), represented by the structural formula (320), with(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)). Here, a weight ratio of YGAPQ toIr(Fdpq)₂(acac) was adjusted to be 1:0.06 (=YGAPQ:Ir(Fdpq)₂(acac)).

After that, bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(abbreviation: BAlq) was formed at a thickness of 10 nm on the lightemitting layer 2105 by the vapor deposition technique using resistanceheating system, thereby forming an electron transporting layer 2106.

Moreover, an electron injecting layer 2107 with a thickness of 50 nm wasformed on the electron transporting layer 2106 by co-evaporation oftris(8-quinolinolato)aluminum (abbreviation: Alq) with lithium. Here, aweight ratio of Alq to lithium was adjusted to be 1:0.01 (=Alq:lithium).

Finally, aluminum was formed at a thickness of 200 nm on the electroninjecting layer 2107 by the vapor deposition technique using resistanceheating system, thereby forming a second electrode 2108. Accordingly, alight-emitting element 3 was fabricated.

(Light-Emitting Element 4)

As an electron transporting layer 2106, tris(8-quinolinolato)aluminum(abbreviation: Alq) was formed at a thickness of 10 nm. Thelight-emitting element 4 was formed in the same manner as thelight-emitting element 3 other than the electron transporting layer.

FIG. 38 shows current density-luminance characteristics of thelight-emitting element 3 and the light-emitting element 4. FIG. 39 showsvoltage-luminance characteristics. FIG. 40 shows luminance-currentefficiency characteristics. FIG. 41 shows voltage-currentcharacteristics. FIG. 42 shows luminance-power efficiencycharacteristics. FIG. 43 shows emission spectra when a current of 1 mAflows. FIG. 43 demonstrates that emission of the light-emitting element3 and the light-emitting element 4 is emission of Ir(Fdpq)₂(acac).

In the light-emitting element 3, the CIE chromaticity coordinates atluminance of 960 cd/m² were (x, y)=(0.71, 0.28), and emission of redlight with excellent color purity was obtained. Current efficiency atluminance of 960 cd/m² was 4.7 cd/A, and external quantum efficiency was12% which were extremely high efficiency. Voltage and current density atluminance of 960 cd/m² were 6.2 V and 20 mA/cm²; respectively, and powerefficiency was 2.4 μm/W which is an extremely high value.

In the light-emitting element 4, the CIE chromaticity coordinates atluminance of 930 cd/m² were (x, y)=(0.65, 0.33), and emission of redlight was obtained. Current efficiency at luminance of 930 cd/m² was 3.6cd/A, and external quantum efficiency was 7.2%, which means that highefficiency is realized. Voltage and current density at luminance of 930cd/m² were 5.8 V and 26 mA/cm², respectively, and power efficiency wasas high as 2.0 lm/W.

FIGS. 39 and 41 show that a driving voltage is reduced in thelight-emitting element 3 and the light-emitting element 4. Accordingly,the use of the quinoxaline derivative of the present invention enablesit to provide a light-emitting element having a low driving voltage andreduced power consumption. In particular, in the light-emitting element3, a driving voltage is further reduced than in the light-emittingelement 4. In addition, as evidenced by FIG. 40, higher currentefficiency is obtained in the light-emitting element 3 than in thelight-emitting element 4. As a result, as shown in FIG. 42, powerefficiency is improved and power consumption is reduced in thelight-emitting element 3 compared with the light-emitting element 4.

FIG. 44 shows time-dependence of normalized luminance of thelight-emitting element 4. FIG. 45 shows change of driving voltage ontime. The measurement was carried out at an initial luminance of 1000cd/m². FIG. 44 shows that change of luminance on time of thelight-emitting element 4 is small. FIG. 45 shows that change of voltageon time of the light-emitting element 4 is small. Therefore, by usingthe quinoxaline derivative of the present invention, a long-lifelight-emitting element can be obtained.

EXAMPLE 6

In this example, a light-emitting element of the present invention willbe explained with reference to FIG. 29.

(Light-Emitting Element 5)

First, indium tin oxide including silicon oxide was formed over a glasssubstrate 2101 by a sputtering method, thereby forming a first electrode2102. It is to be noted that a thickness thereof was 110 nm and anelectrode area was 2 mm×2 mm.

Next, the substrate, over which the first electrode was formed, wasfixed to a substrate holder in a vacuum evaporation apparatus so thatthe side, on which the first electrode was formed, faced downward.Subsequently, a layer 2103 including a composite of an organic compoundwith an inorganic compound was formed on the first electrode 2102 byco-evaporation of NPB with molybdenum oxide (VI) after the pressure ofthe evaporation apparatus was reduced to approximately 10⁻⁴ Pa. Athickness thereof was adjusted to be 50 nm and a weight ratio of NPB tomolybdenum oxide (VI) was adjusted to be 4:1 (=NPB:molybdenum oxide). Itis to be noted that the co-evaporation method is an evaporation methodby which evaporation is performed simultaneously from a plurality ofevaporation sources in one evaporation chamber.

Next, 4,4′-bis[N-(1-napthyl)-N-phenylamino]biphenyl (abbreviation: NPB)was deposited at the thickness of 10 nm over the composite-includinglayer 2103 by the vapor deposition technique using resistance heatingsystem, leading to the formation of a hole transporting layer 2104.

Furthermore, a light emitting layer 2105 with a thickness of 30 nm wasformed on the hole transporting layer 2104 by co-evaporation ofN,N′-(quinoxaline-2,3-diyldi-4,1-phenylene)bis(N-phenyl-9-phenylcarbazole-3-amine)(abbreviation: PCAPQ) with(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)). Here, a weight ratio of PCAPQ toIr(Fdpq)₂(acac) was adjusted to be 1:0.08 (=PCAPQ:Ir(Fdpq)₂(acac)).

After that, tris(8-quinolinolato)aluminum (abbreviation: Alq) was formedat a thickness of 10 nm on the light emitting layer 2105 by the vapordeposition technique using the resistance heating system, therebyforming an electron transporting layer 2106.

Moreover, an electron injecting layer 2107 with a thickness of 50 nm wasformed on the electron transporting layer 2106 by co-evaporation oftris(8-quinolinolato)aluminum (abbreviation: Alq) with lithium. Here, aweight ratio of Alq to lithium was adjusted to be 1:0.01 (=Alq:lithium).

Finally, aluminum Was formed at a thickness of 200 nm on the electroninjecting layer 2107 by the vapor deposition technique using theresistance heating system, thereby forming a second electrode 2108.Accordingly, a light-emitting element 5 was fabricated.

FIG. 46 shows current density-luminance characteristics of thelight-emitting element 5. FIG. 47 shows voltage-luminancecharacteristics. FIG. 48 shows luminance-current efficiencycharacteristics. FIG. 49 shows voltage-current characteristics. FIG. 50shows an emission spectrum of the light-emitting element 5 when acurrent of 1 mA flows. FIG. 50 indicates that emission of thelight-emitting element 5 is emission of Ir(Fdpq)₂(acac). The CIEchromaticity coordinates at luminance of 1100 cd/m² were (x, y)=(0.69,0.30), and emission of red light with excellent color purity wasobtained. Current efficiency at luminance of 1100 cd/m² was as high as2.1 cd/A. Voltage and current density at luminance of 1100 cd/m² were5.0 V and 51 mA/cm², respectively. The power efficiency, 1.3 lm/W,reveals that high power efficiency is achieved. Further, FIGS. 47 and 49show that the driving voltage is reduced in the light-emitting element5. Therefore, the use of the quinoxaline derivative of the presentinvention makes it possible to fabricate a light-emitting element withlow driving voltage and reduced power consumption.

EXAMPLE 7

In this example, a synthetic method ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ) that is a quinoxaline derivative of the presentinvention represented by a structural formula (86) will be specificallyshown.

[Step 1]Synthesis ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(Abbreviation: PCA1PQ)

A synthetic scheme ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ) is shown in (H-1).

2.0 g (5.5 mmol) of 2-(4-bromophenyl)-3-phenylquinoxaline, 2.0 g ofsodium tert-butoxide, 1.9 g (5.5 mmol) ofN-phenyl-(9-phenylcarbazol-3-yl)amine (abbreviation: PCA), and 0.1 g(0.2 mmol) of bis(dibenzylideneacetone)palladium(0) were put into a100-mL three-neck flask, and nitrogen substitution was carried out inthe flask. Then, 30 mL of toluene and 0.1 mL of a 10% hexane solution oftri-tert-butylphosphine were added to the mixture, and the mixture washeated and stirred at 80° C. for 3 hours. After the reaction, toluenewas added to the reaction mixture, and the suspension was subjected tosuction filtration through florisil, celite, and alumina, and thefiltrate was obtained. The obtained filtrate washed with water, andthen, the water phase and the organic phase were separated from eachother. Magnesium sulfate was added to the organic phase for drying. Themixture was subjected to suction filtration to remove magnesium sulfate,the obtained filtrate was concentrated, and a solid was obtained. Theobtained solid was recrystallized with a mixed solvent of chloroform andhexane. 2.5 g of a yellow solid was obtained in the yield of 73%. It wasconfirmed by a nuclear magnetic resonance method (NMR) that thiscompound wasN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ).

¹H NMR data of this compound is shown below.

¹H NMR (CDCl₃, 300 MHz): δ=6.96-7.66 (m, 24H), 7.66-7.78 (m, 2H),7.91-7.96 (m, 1H), 7.98 (d, J=7.8 Hz, 1H), 8.10-8.19 (m, 2H).

FIGS. 55A and 55B each show a ¹H NMR chart. FIG. 55B shows an expandedchart of FIG. 55A in a range of 6.5 ppm to 8.5 ppm.

Then, sublimation purification of the obtained yellow solid wasperformed by a train sublimation method. The sublimation purificationwas performed at 295° C. for 12 hours under a reduced pressure of 7 Pa,setting the flow rate of argon to be 3 mL/min. When sublimationpurification was performed on 2.5 g of charged PCA1PQ, the yield was 2.1g (84%).

FIG. 56 shows an absorption spectrum of a toluene solution of PCA1PQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The solution was put into aquartz cell, and the absorption spectrum thereof, from which theabsorption spectrum of quartz was subtracted, is shown in FIG. 56. InFIG. 56, the horizontal axis indicates the wavelength (nm) and thevertical axis indicates the absorption intensity (arbitrary unit). Theabsorption was observed at around 315 nm and at around 411 nm in thecase of the toluene solution. FIG. 57 shows the emission spectrum of thetoluene solution (the excitation wavelength: 410 nm) of PCA1PQ. In FIG.57, the horizontal axis indicates the wavelength (nm) and the verticalaxis indicates the emission intensity (arbitrary unit). The maximumemission wavelength was 521 nm (the excitation wavelength: 410 nm) inthe case of the toluene solution.

FIG. 73 shows an absorption spectrum of a thin film of PCA1PQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The thin film sample ofPCA1PQ was formed on a quartz substrate by the vapor depositiontechnique, and the absorption spectrum thereof, from which theabsorption spectrum of quartz was subtracted, is shown in FIG. 73. InFIG. 73, the horizontal axis indicates the wavelength (nm) and thevertical axis indicates the absorption intensity (arbitrary unit). Theabsorption was observed at around 423 nm in the case of the thin film.FIG. 74 shows the emission spectrum of the thin film (the excitationwavelength: 423 nm) of PCA1PQ. In FIG. 74, the horizontal axis indicatesthe wavelength (nm) and the vertical axis indicates the emissionintensity (arbitrary unit). The maximum emission wavelength was 552 nm(the excitation wavelength: 423 nm) in the case of the thin film.

The result of measuring the thin-film using a photoelectron spectrometer(AC-2, manufactured by Riken Keiki Co., Ltd.) under the atmosphereindicated that the HOMO level of PCA1PQ in the solid state is −5.22 eV.The Tauc plot of the absorption spectrum shown in FIG. 73 revealed thatthe absorption edge was 2.59 eV. Thus, the energy gap of PCA1PQ in thesolid state was estimated to be 2.59 eV, which means that the LUMO levelof PCA1PQ in the solid state is −2.63 eV.

EXAMPLE 8

In this example, a synthetic method ofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ) that is a quinoxaline derivative of the presentinvention represented by a structural formula (21) will be specificallyshown.

[Step 1]Synthesis ofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(Abbreviation: DPA1PQ)

A synthetic scheme ofN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ) is shown in (J-1).

1.0 g (2.8 mmol) of 2-(4-bromophenyl)-3-phenylquinoxaline, 0.3 g ofsodium tert-butoxide, 0.93 g (2.8 mmol) ofN,N′,N′-triphenyl-1,4-phenylenediamine, and 0.05 g (0.1 mmol) ofbis(dibenzylideneacetone)palladium(0) were put into a 50-mL three-neckflask, and nitrogen substitution was carried out in the flask. Then, 20mL of toluene and 0.05 mL of a 10% hexane solution oftri-tert-butylphosphine were added to the mixture, and the mixture washeated and stirred at 80° C. for 3 hours. After the reaction, toluenewas added to the reaction mixture, and the suspension was subjected tosuction filtration through florisil, celite, and alumina. The obtainedfiltrate washed with a sodium hydrogencarbonate aqueous solution andbrine in this order, and then, a water phase and an organic phase wereseparated from each other. Magnesium sulfate was added to the organicphase for drying. The mixture was subjected to suction filtration toremove magnesium sulfate, the obtained filtrate was concentrated, andthe resulting solid was obtained. The obtained solid was recrystallizedwith a mixed solvent of chloroform and methanol. 1.4 g of a yellow solidwas obtained in the yield of 78%. It was confirmed by a nuclear magneticresonance method (NMR) that this compound wasN,N′,N′-triphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]benzene-1,4-diamine(abbreviation: DPA1PQ).

¹H NMR data of this compound is shown below.

¹H NMR (CDCl₃, 300 MHz): δ=6.93-7.43 (m, 26H), 7.55-7.62 (m, 2H),7.71-7.77 (m, 2H), 8.11-8.19 (m, 2H).

FIGS. 58A and 58B each show a ¹H NMR chart. FIG. 58B shows an expandedchart of FIG. 58A in a range of 6.5 ppm to 8.5 ppm.

Then, sublimation purification of the obtained yellow solid wasperformed by a train sublimation method. The sublimation purificationwas performed at 266° C. for 15 hours under a reduced pressure of 7 Pa,setting the flow rate of argon to be 3 mL/min. When sublimationpurification was performed on 1.4 g of charged DPA1PQ, the yield was 1.1g (79%).

FIG. 59 shows an absorption spectrum of a toluene solution of DPA1PQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The solution was put into aquartz cell, and the absorption spectrum thereof, from which theabsorption spectrum of quartz was subtracted, is shown in FIG. 59. InFIG. 59, the horizontal axis indicates the wavelength (nm) and thevertical axis indicates the absorption intensity (arbitrary unit). Theabsorption was observed at around 325 nm and at around 410 nm in thecase of the toluene solution. FIG. 60 shows the emission spectrum of thetoluene solution (the excitation wavelength: 410 nm) of DPA1PQ. In FIG.60, the horizontal axis indicates the wavelength (nm) and the verticalaxis indicates the emission intensity (arbitrary unit). The maximumemission wavelength was 559 nm (the excitation wavelength: 410 nm) inthe case of the toluene solution.

FIG. 75 shows an absorption spectrum of a thin film of DPA1PQ. Anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation) was used for the measurement. The thin film was prepared asa sample by the vapor deposition of DPA1PQ on a quartz substrate, andthe absorption spectrum thereof, from which the absorption spectrum ofquartz was subtracted, is shown in FIG. 75. In FIG. 75, the horizontalaxis indicates the wavelength (nm) and the vertical axis indicates theabsorption intensity (arbitrary unit). The absorption was observed ataround 421 nm in the case of the thin film. FIG. 76 shows the emissionspectrum of a thin film (the excitation wavelength: 421 nm) of DPA1PQ.In FIG. 76, the horizontal axis indicates the wavelength (nm) and thevertical axis indicates the emission intensity (arbitrary unit). Themaximum emission wavelength was 566 nm (the excitation wavelength: 421nm) in the case of the thin film.

The result of measuring the thin-film using a photoelectron spectrometer(AC-2, manufactured by Riken Keiki Co., Ltd.) under the atmosphereindicated that the HOMO level of DPA1PQ in the solid state is −5.31 eV.The Tauc plot of the absorption spectrum shown in FIG. 75 revealed thatthe absorption edge was 2.60 eV. Thus, the energy gap of DPA1PQ in thesolid state was estimated to be 2.60 eV, which means that the LUMO levelof PCA1PQ in the solid state is −2.71 eV.

EXAMPLE 9

In this example, a light-emitting element of the present invention willbe explained with reference to FIG. 29.

(Light-Emitting Element 6)

First, indium tin oxide including silicon oxide was formed over a glasssubstrate 2101 by a sputtering method, thereby forming a first electrode2102. It is to be noted that a thickness thereof was 110 nm and anelectrode area was 2 mm×2 mm.

Next, the substrate, over which the first electrode was formed, wasfixed to a substrate holder in a vacuum evaporation apparatus so thatthe side, on which the first electrode was formed, faced downward.Subsequently, a layer 2103 including a composite of an organic compoundwith an inorganic compound was formed on the first electrode 2102 byco-evaporation of NPB and molybdenum oxide (VI) after a pressure of thevacuum evaporation apparatus was reduced to approximately 10⁻⁴ Pa. Athickness thereof was adjusted to be 50 nm and a weight ratio of NPB tomolybdenum oxide (VI) was adjusted to be 4:1 (=NPB:molybdenum oxide). Itis to be noted that the co-evaporation method is an evaporation methodin which evaporation is performed simultaneously from a plurality ofevaporation sources in one evaporation chamber.

Next, 4,4′-bis[N-(1-napthyl)-N-phenylamino]biphenyl (abbreviation: NPB)was deposited at the thickness of 10 nm over the composite-includinglayer 2103 by the vapor deposition technique using resistance heatingsystem, leading to the formation of a hole transporting layer 2104.

Further, a light emitting layer 2105 with a thickness of 30 nm wasformed on the hole transporting layer 2104 by co-evaporation of4-(carbazol-9-yl)-4′-(3-phenylquinoxalin-2-yl)triphenylamine(abbreviation: YGA1PQ) represented by the structural formula (159) with(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)). Here, a weight ratio of YGA1PQ andIr(Fdpq)₂(acac) was adjusted to be 1:0.06 (=YGA1PQ:Ir(Fdpq)₂(acac)).

After that, bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(abbreviation: BAlq) was formed at a thickness of 10 nm on the lightemitting layer 2105 by the vapor deposition technique using resistanceheating system, thereby forming an electron transporting layer 2106.

Moreover, an electron injecting layer 2107 with a thickness of 50 nm wasformed on the electron transporting layer 2106 by co-evaporation oftris(8-quinolinolato)aluminum (abbreviation: Alq) with lithium. Here, aweight ratio of Alq to lithium was adjusted to be 1:0.01 (=Alq:lithium).

Finally, aluminum was formed at a thickness of 200 nm on the electroninjecting layer 2107 by the vapor deposition technique using resistanceheating system, thereby forming a second electrode 2108. Accordingly, alight-emitting element 6 was fabricated.

FIG. 61 shows current density-luminance characteristics of thelight-emitting element 6. FIG. 62 shows voltage-luminancecharacteristics. FIG. 63 shows luminance-current efficiencycharacteristics. FIG. 64 shows voltage-current characteristics. FIG. 65shows an emission spectrum of the light emitting element 6 when acurrent of 1 mA flows. FIG. 65 indicates that emission of thelight-emitting element 6 is emission of Ir(Fdpq)₂(acac). The CIEchromaticity coordinates at luminance of 960 cd/m² were (x, y)=(0.71,0.29), and emission of red light with excellent color purity wasobtained. Current efficiency at luminance of 960 cd/m² was 6.3 cd/A, andexternal quantum efficiency was as high as 14%. Voltage and currentdensity at luminance of 960 cd/m² were 6.0 V and 15 mA/cm²,respectively, and power efficiency was 3.3 lm/W which was an extremelyhigh value. Further, FIGS. 62 and 64 show that a driving voltage isreduced in the light-emitting element 6. Therefore, the use of thequinoxaline derivative of the present invention allows the fabricationof a light-emitting element having a low driving voltage and reducedpower consumption.

EXAMPLE 10

In this example, a light-emitting element of the present invention willbe explained with reference to FIG. 29.

(Light-Emitting Element 7)

First, indium tin oxide including silicon oxide was formed over a glasssubstrate 2101 by a sputtering method, thereby forming a first electrode2102. It is to be noted that a thickness thereof was 110 nm and anelectrode area was 2 mm×2 mm.

Next, the substrate, over which the first electrode was formed, wasfixed to a substrate holder in a vacuum evaporation apparatus so thatthe side, on which the first electrode was formed, faced downward.Subsequently, a layer 2103 including a composite of an organic compoundwith an inorganic compound was formed on the first electrode 2102 byco-evaporation of NPB and molybdenum oxide (VI) after a pressure of thevacuum evaporation apparatus was reduced to approximately 10⁻⁴ Pa. Athickness thereof was adjusted to be 50 nm and a weight ratio of NPB tomolybdenum oxide (VI) was adjusted to be 4:1 (=NPB:molybdenum oxide). Itis to be noted that the co-evaporation method is an evaporation methodin which evaporation is performed simultaneously from a plurality ofevaporation sources in one treatment chamber.

Next, 4,4′-bis[N-(1-napthyl)-N-phenylamino]biphenyl (abbreviation: NPB)was deposited at the thickness of 10 nm over the composite-includinglayer 2103 by the vapor deposition technique using resistance heatingsystem, leading to the formation of a hole transporting layer 2104.

Further, a light emitting layer 2105 with a thickness of 30 nm wasformed on the hole transporting layer 2104 by co-evaporation ofN-phenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9-phenylcarbazole-3-amine(abbreviation: PCA1PQ) represented by the structural formula (86) with(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)). Here, a weight ratio of PCA1PQ andIr(Fdpq)₂(acac) was adjusted to be 1:0.06 (=PCA1PQ:Ir(Fdpq)₂(acac)).

After that, bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(abbreviation: BAlq) was formed at a thickness of 10 nm on the lightemitting layer 2105 by the vapor deposition technique using resistanceheating system, thereby forming an electron transporting layer 2106.

Moreover, an electron injecting layer 2107 with a thickness of 50 nm wasformed on the electron transporting layer 2106 by co-evaporation oftris(8-quinolinolato)aluminum (abbreviation: Alq) with lithium. Here, aweight ratio of Alq to lithium was adjusted to be 1:0.01 (=Alq:lithium).

Finally, aluminum was formed at a thickness of 200 nm on the electroninjecting layer 2107 by the vapor deposition technique using resistanceheating system, thereby forming a second electrode 2108. Accordingly, alight-emitting element 6 was manufactured.

FIG. 66 shows current density-luminance characteristics of thelight-emitting element 7. FIG. 67 shows voltage-luminancecharacteristics. FIG. 68 shows luminance-current efficiencycharacteristics. FIG. 69 shows voltage-current characteristics. FIG. 70shows an emission spectrum of the light-emitting element 7 when acurrent of 1 mA flows. FIG. 70 indicates that emission of thelight-emitting element 7 is emission of Ir(Fdpq)₂(acac). The CIEchromaticity coordinates at luminance of 1100 cd/m were (x, y)=(0.70,0.30), and emission of red light with excellent color purity wasobtained. Current efficiency at luminance of 1100 cd/m² was 4.3 cd/A,and external quantum efficiency was 7.4%, which means that highefficiency is attainable. Voltage and current density at luminance of1100 cd/m² were 4.8 V and 25 mA/cm², respectively, and power efficiencywas 2.8 lm/W which was an extremely high value. Further, FIGS. 67 and 69show that a driving voltage is reduced in the light-emitting element 7.Therefore, by using the quinoxaline derivative of the present invention,a light-emitting element with a low driving voltage and reduced andpower consumption can be obtained.

EXAMPLE 11

In this example, a material used in the aforementioned examples will beexplained.

<<Synthesis of Ir(tppr)₂(acac)>>

Hereinafter, an example for the synthesis of(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]) represented by a structural formula(402) will be specifically exemplified.

[Step 1]

Synthesis of 2,3,5-triphenylpyrazine (abbreviation: Htppr) will beexplained.

First, in a nitrogen atmosphere, 5.5 mL of a dibutyl ether solution ofphenyl lithium (produced by Wako Pure Chemical Industries, Ltd., 2.1mol/L) and 50 mL of diethyl ether were mixed to prepare a solution.Then, 2.43 g of 2,3-diphenylpyrazine was dropwised into this solutionwhile the solution was being cooled with ice, and the mixture wasstirred at room temperature for 24 hours. After the stirring, water wasadded to the mixture and the organic phase was extracted with diethylether. The extracted organic phase washed with water and dried withmagnesium sulfate. After the drying, to the organic layer was added anexcess amount of activated manganese dioxide, and the mixture wasstirred sufficiently, and then filtered. After a solvent of the filtratewas distilled off, the obtained residue was recrystallized with ethanolto give a pyrazine derivative, Htppr (yellow powder), in the yield of56%. A synthetic scheme of Step 1 is shown in the following (G-1).

[Step 2]

Synthesis of di-μ-chloro-bis[bis(2,3,5-triphenylpyrazinato)iridium(III)](abbreviation: [Ir(tppr)₂Cl]₂) will be explained.

1.08 g of the pyrazine derivative Htppr obtained in the above Step 1 and0.73 g of iridium chloride hydrate (IrCl₃.H₂O) (produced bySigma-Aldrich Corp.) were mixed in a mixed solvent of 30 mL of2-ethoxyethanol and 10 mL of water, and the mixture was refluxed in anitrogen atmosphere for 16 hours. The precipitated powder was filteredand washed with ethanol, ether, and then hexane, giving a dinuclearcomplex [Ir(tppr)₂Cl]₂ (orange powder) in the yield of 97%. A syntheticscheme of Step 2 is shown in the following (G-2).

[Step 3]

Synthesis of (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]) will be explained.

2.00 g of the dinuclear complex [Ir(tppr)₂Cl]₂ obtained in the aboveStep 2, 0.37 mL of acetylacetone, and 1.26 g of sodium carbonate weremixed in a solvent of 40 mL of 2-ethoxyethanol, and the mixture wasrefluxed under a nitrogen atmosphere for 18 hours. After the reflux, themixture was filtered and the filtrate was left for one week. Then, theprecipitated crystal was removed by filtration and the solvent of thefiltrate was distilled off. The obtained residue was recrystallized witha mixed solvent of dichloromethane and ethanol. A powder obtained by therecrystallization washed with ethanol and then ether, giving theorganometallic complex [Ir(tppr)₂(acac)] (orange powder) in the yield of16%. A synthetic scheme of Step 3 is shown in the following (G-3).

An analysis result of the orange powder obtained in the above Step 3 bynuclear magnetic resonance spectrometry (¹H NMR) is shown below. FIGS.53A and 53B each show a ¹H NMR chart. FIG. 53B shows an expanded view ofFIG. 53A in the vertical axis direction. From FIGS. 53A and 53B, it wasconfirmed that the organometallic complex [Ir(tppr)₂(acac)] representedby the above structural formula (402) was obtained in this SynthesisExample 1.

¹H NMR (CDCl₃, 300 MHz): δ=1.92 (s, 6H), 5.35 (s, 1H), 6.45-6.54 (m,4H), 6.67 (td, 2H), 6.91 (d, 2H), 7.41-7.57 (m, 12H), 7.81 (m, 4H), 8.08(dd, 4H), 8.98 (s, 2H).

Further, a decomposition temperature, T_(d), of the obtainedorganometallic complex [Ir(tppr)₂(acac)] measured by athermo-gravimetric/differential thermal analyzer (TG/DTA 320,manufactured by Seiko Instruments Inc.) was 331° C. Therefore, it wasfound that [Ir(tppr)₂(acac)] shows excellent thermal stability.

Next, an absorption spectrum of [Ir(tppr)₂(acac)] was measured using anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation). The measurement was conducted by using a degasseddichloromethane solution (0.10 mmol/L) at a room temperature. Inaddition, an emission spectrum of [Ir(tppr)₂(acac)] was measured using afluorescence spectrophotometer (FS920, manufactured by HamamatsuPhotonics Corporation). The measurement was conducted by using adegassed dichloromethane solution (0.35 mmol/L) at room temperature.FIG. 54 shows the measurement results. The horizontal axis indicates awavelength and the vertical axis indicates a molar absorptioncoefficient and emission intensity.

As shown in FIG. 54, the organometallic complex [Ir(tppr)₂(acac)] has apeak of emission at 622 nm, and emission of red-orange light wasobserved from the solution.

It was revealed that the organometallic complex [Ir(tppr)₂(acac)] hasseveral absorption peaks in the visible light region. This is absorptionunique to some organometallic complexes such as an ortho-metalatedcomplex, and is considered to correspond to singlet MLCT transition,triplet π-π* transition, triplet MLCT transition, or the like. Inparticular, the absorption on the longest wavelength side is tailingtoward the long-wavelength region. Thus, this absorption is consideredto correspond to the triplet MLCT transition. In other words, it wasconfirmed that the organometallic complex [Ir(tppr)₂(acac)] was acompound capable of direct photo-excitation to a triplet excited stateand intersystem crossing. Therefore, it can be considered that obtainedemission was light emission from the triplet excited state, in otherwords, phosphorescence.

[Step 4]

A synthetic method of 2,3,5-triphenylpyrazine (abbreviation: Htppr),which was synthesized in the above Step 1, different from Step 1 will beexemplified.

First, 4.60 g of phenylglyoxal (produced by Tokyo Chemical IndustriesCo., Ltd.) and 7.28 g of meso-1,2-diphenylethylenediamine were mixed ina solvent of 200 mL of ethanol, and the mixture was refluxed in anitrogen atmosphere for 6 hours. After the reflux, the solvent of thismixture was distilled off, and the obtained residue was recrystallizedwith ethanol. An ocher powder obtained by the recrystallization wasdissolved into dichloromethane, and an excess amount of manganesedioxide was added to the solution. The mixture was stirred sufficiently,and then filtered. After a solvent of the filtrate was distilled off,the obtained residue was recrystallized with ethanol, giving a pyrazinederivative, Htppr (yellow powder), in the yield of 37%. A syntheticscheme of Step 4 is shown in the following (G-1-2).

This application is based on Japanese Patent Application serial No.2006-077900 filed in Japan Patent Office on Mar. 21, 2006, the contentsof which are hereby incorporated by reference.

EXPLANATION OF REFERENCE

101: substrate, 102: first electrode, 103: first layer, 104: secondlayer, 105: third layer, 106: fourth layer, 107: second electrode, 301:substrate, 302: first electrode, 303: first layer, 304: second layer,305: third layer, 306: fourth layer, 307: second electrode, 501: firstelectrode, 502: second electrode, 511: first light-emitting unit, 512:second light-emitting unit, 513: charge generation layer, 601: sourceside driver circuit, 602: pixel portion, 603: gate side driver circuit,604: sealing substrate, 605: sealing material, 607: space, 608: wiring,609: FPC (flexible printed circuit), 610: element substrate, 611:switching TFT, 612: current control TFT, 613: first electrode, 614:insulator, 616: layer including light-emitting substance, 617: secondelectrode, 618: light-emitting element, 623: n-channel TFT, 624:p-channel TFT, 901: housing, 902: liquid crystal layer, 903: backlight,904: housing, 905: driver IC, 906: terminal, 951: substrate, 952:electrode, 953: insulating layer, 954: partition layer, 955: layerincluding light-emitting substance, 956: electrode, 1201: sourceelectrode, 1202: active layer, 1203: drain electrode, 1204: gateelectrode, 2001: housing, 2002: light source, 2101: substrate, 2102:first electrode, 2103: layer including composite material, 2104: holetransporting layer, 2105: light emitting layer, 2106: electrontransporting layer, 2107: electron injecting layer, 2108: secondelectrode, 9101: housing, 9102: supporting base, 9103: display portion,9104: speaker portion, 9105: video input terminal, 9201: main body,9202: housing, 9203: display portion, 9204: keyboard, 9205: externalconnection port, 9206: pointing mouse, 9401: main body, 9402: housing,9403: display portion, 9404: audio input portion, 9405: audio outputportion, 9406: operation key, 9407: external connection port, 9408:antenna, 9501: main body, 9502: display portion, 9503: housing, 9504:external connection port, 9505: a remote control receiving portion,9506: image receiving portion, 9507: battery, 9508: audio input portion,9509: operation key, 9510: eye piece portion

1. A compound represented by the structure:

wherein: R¹ to R⁴ each represent any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; R⁵ represents any of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; Ar¹represents an aryl group having 6 to 25 carbon atoms, α represents anarylene group having 6 to 25 carbon atoms; A is represented by thestructure:

γ represents an arylene group having 6 to 25 carbon atoms; and R⁴¹ andR⁴² each represent any of a hydrogen atom, an alkyl group having 1 to 4carbon atoms, or an aryl group having 6 to 25 carbon atoms.
 2. Acompound according to claim 1, wherein: A is represented by thestructure:

R⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; andR⁴³ to R⁴⁶ each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 15 carbon atoms.
 3. Acompund according to claim 1, wherein: Ar¹ is represented by thestructure:

R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 15 carbon atoms; A isrepresented by the structure:

R⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; andR⁴³ to R⁴⁶ each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 15 carbon atoms.
 4. Acompund according to claim 1, wherein: α is represented by thestructure:

Ar¹ is represented by the structure:

R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 15 carbon atoms; A isrepresented by the structure:

R⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; andR⁴³ to R⁴⁶ each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 15 carbon atoms.
 5. Acompound according to claim 1, wherein: R¹ to R⁴ each represent ahydrogen atom; R⁵ represents any of a hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbonatoms; α is represented by the structure:

Ar¹ is represented by the structure:

R⁶ to R¹⁰ each represent any of a hydrogen atom, an alkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 15 carbon atoms; A isrepresented by the structure:

R⁴¹ and R⁴² each represent any of a hydrogen atom, an alkyl group having1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms.